ad-libitum
ad-libitum copied to clipboard
ul
Scheme Live Coding Environment
#+TITLE: Ad Libitum #+SETUPFILE: org-html-themes/org/theme-readtheorg.setup
The Scheme Live Coding Environment. Built on Chez Scheme and libsoundio.
You might want to read this file here [[http://ul.mantike.pro/ad-libitum/README.html]]
-
Getting Started
This guide describes initial setup required to produce your first piece of digital noise with Ad Libitum. At the moment Ad Libitum is tested only on MacOS therefore following instructions are MacOS-specific. Any feedback and improvement for other platforms is more than welcome! Current state of Ad Libitum dependencies is that it should be easy to port it to Linux and moderately hard (but possible) to Windows.
** Chez Scheme
First, you need Chez Scheme itself. Ad Libitum requires threaded version and you probably don't want to install x11 dependency, that's why better to do it from source, not brew. Also we are using Racket's fork to be able to build on M1 while https://github.com/cisco/ChezScheme/issues/544 is in progress.
*** Clone Chez Scheme repository
#+BEGIN_SRC shell git clone https://github.com/racket/ChezScheme.git cd ChezScheme #+END_SRC
*** Configure, build and install Chez Scheme
#+BEGIN_SRC shell ./configure --disable-x11 make sudo make install #+END_SRC
The first command may suggest you to build boot image first, e.g. on M1: #+begin_src shell ./configure --pb make tarm64osx.bootquick #+end_src
*** Test it's working
Run =scheme= from terminal and try to evaluate simple expression:
#+BEGIN_SRC shell ~/ChezScheme> scheme
Chez Scheme Version 9.5.5.5 Copyright 1984-2020 Cisco Systems, Inc.
(+ 1 2 3) 6
#+END_SRC
** libsoundio
This is library used by Ad Libitum for communication with your computer's sound system.
#+BEGIN_SRC shell brew install libsoundio #+END_SRC
** PortMidi
You need it if you plan to use MIDI controller.
#+BEGIN_SRC shell brew install portmidi #+END_SRC
** Ad Libitum itself
*** Install
You need to clone repository and build several helping libraries. You may need to set ~SCHEMEH~ environment variable to your platform-specific location (default value is ~/usr/local/lib/csv9.5.5.5/tarm64osx/~).
#+BEGIN_SRC shell git clone https://github.com/ul/ad-libitum.git cd ad-libitum git submodule update --init --recursive --remote make libs #+END_SRC
*** Test
Fire up =scheme ad-libitum.ss= and play 440Hz tuner (beware of loud sound!
reduce speakers/headphones volume before running). Congratulations, you
livecoded your first Ad Libitum piece!
#+BEGIN_SRC scheme ~/ad-libitum> scheme ad-libitum.ss
Chez Scheme Version 9.5.1 Copyright 1984-2017 Cisco Systems, Inc.
(play! tuner)
#+END_SRC
*** Play
Run & =geiser-connect=
#+BEGIN_SRC shell scheme --optimize-level 2 violet.ss #+END_SRC
- Contribution
Contribution is more than welcome and highly appreciated! Any small or non-code fix is valuable as well, including spelling and grammar and setting proper licensing.
- Kernel
** Sound I/O
Ad Libitum relies on =chez-soundio= bindings and high-level wrapper. We are going to create and open default i/o (only 'o' at the moment) stream and provide it globally.
For performance reasons =chez-sound= itself doesn't provide any protection against broken =write-callback=. But in livecoding mistakes are the part of exploration and arguably we want to sacrifice some performance to be able to not restart entire sound subsystem for fixing our =write-callback=. That's why calling =dsp= is wrapped into =guard=.
To keep our scheduler clock in sync with audio we store audio time and return it from =now= function which is passed to scheduler later.
#+NAME: sound
#+BEGIN_SRC scheme
;;
(define (silence time channel) 0.0) (define dsp silence) (define (set-dsp! f) (set! dsp f)) (define (hush!) (set-dsp! silence))
(define (write-callback time channel) (set! time time) (guard (_ [else 0.0]) (dsp time channel)))
(define sound-out (soundio:open-default-out-stream write-callback)) (define sample-rate (soundio:sample-rate sound-out)) (define channels (soundio:channel-count sound-out))
(define (start) (soundio:start-out-stream sound-out)) (define (stop) (soundio:stop-out-stream sound-out)) ;; #+END_SRC
** Scheduler
Much of music is about time. Before we produce any single sample of wave, we want to control when to start and when to stop doing it. Much of live coding is about decoupling our commands from their execution. We want to say "play note a second later" now, but play it a second later. It's where scheduler comes to play. Essentially, scheduler's API is simple and allows to get current time mark (whatever it means: system clock, time elapsed from scheduler start or number of rendered samples) and to callback procedure at some point of time with more or less guaranteed skew limit.
Let's start with scheduler interface. As has been said there are two basic functions it must provide, =now= and =schedule=. First one allows to get current point in time, and it is usually comes to schedule from external source like audio stream to be in sync with it. Second one allows to schedule execution at some point in future.
#+NAME: scheduler-interface
#+BEGIN_SRC scheme
;;
As far as scheduler is stateful and even involves thread creation, it must have two other basic methods:
#+NAME: scheduler-interface
#+BEGIN_SRC scheme
;;
Let's shape scheduler's data. Obviously, =now= appears here, in form of either scheduler's own counter or function (which will get system time or related write thread sample number). Another thing is =queue=, where =schedule= will store callbacks. Because queuing could happen from different threads at the same time, as well as dequeuing inside scheduler could happen together with queuing from another thread, we need to protect it with =mutex=. We also need =thread= id or flag or whatever used to control thread exit, because Scheme doesn't expose =pthread_kill=. And the last one which comes to the mind at the moment is =resolution= as a number of times per second scheduler checks the =queue= for expired events.
Together with record definition we provide =simple-scheduler= which creates schedule with reasonable default parameters. The only thing it accepts is =now=, because usually you want you schedule to be in sync with external clock.
#+NAME: scheduler-record
#+BEGIN_SRC scheme
;;
(define (simple-scheduler now) (make-scheduler now ; now heap/empty ; queue 250 ; resolution #f ; thread (make-mutex) ; mutex )) ;; #+END_SRC
Let's implement scheduler interface.
=now= then would just call =now= field:
#+NAME: now
#+BEGIN_SRC scheme
;;
Event queue accepts events which must have =f= with its =args= to execute at =time=:
#+NAME: event-record
#+BEGIN_SRC scheme
;;
For =queue= we need some heap implementation, I'm going to jump into [[Pairing Heap]]!
Mutex is used to prevent data race on insert and remove from queue happening in different threads.
=schedule= should accept either =event= record, or its fields (and create record by itself) to unclutter user code.
#+NAME: schedule
#+BEGIN_SRC scheme
;;
Processing events is just executing any expired events' functions and removing them from the queue.
To enable dynamic temporal recursion we support event's =f= to be a symbol referring top level function.
Of course, live events are error prone, but we don't want flawed event to blow entire thread. Thus =f= execution is secured with =guard=.
#+NAME: scheduler-process-events
#+BEGIN_SRC scheme
;;
Now it's a time for start/stop thread. Stopping thread would be just setting a flag which I used to call "poison pill".
#+NAME: stop-scheduler
#+BEGIN_SRC scheme
;;
Starting thread will fork and loop calling expired events. We set expire period for a half of resolution period in future to compensate a little bit that events could expire during =process-events=. Proper adjustment require further investigation taking in account that audio clock is not uniform (it moves fast inside filling audio buffer process then waits to buffer to be available again).
#+NAME: start-scheduler
#+BEGIN_SRC scheme
;;
#+NAME: scheduler
#+BEGIN_SRC scheme
;;
We need just a simple default scheduler at hand for Ad Libitum needs:
#+NAME: easy-scheduler #+BEGIN_SRC scheme (define scheduler #f) (define (init now) (set! scheduler (simple-scheduler now))) (define (start) (start-scheduler scheduler)) (define (stop) (stop-scheduler scheduler)) (define (schedule t f . args) (schedule scheduler (make-event t f args))) (define (now) (now scheduler)) #+END_SRC
*** Pairing Heap
Wikipedia's type definition for pairing heap structure looks like Scheme's pairs (surprise =) ). Using them implementation is quite straightforward.
#+NAME: pairing-heap
#+BEGIN_SRC scheme
;;
(define heap/empty '())
(define (heap/find-min heap) (if (null? heap) #f (car heap)))
(define (heap/merge comparator h1 h2) (cond [(null? h1) h2] [(null? h2) h1] [(< (comparator (car h1)) (comparator (car h2))) (cons (car h1) (cons h2 (cdr h1)))] [else (cons (car h2) (cons h1 (cdr h2)))]))
(define (heap/insert comparator elem heap) (heap/merge comparator (cons elem '()) heap))
(define (heap/merge-pairs comparator subheaps) (cond [(null? subheaps) heap/empty] [(null? (cdr subheaps)) (car subheaps)] [else (heap/merge comparator (heap/merge comparator (car subheaps) (cadr subheaps)) (heap/merge-pairs comparator (cddr subheaps)))]))
(define (heap/delete-min comparator heap) (if (null? heap) heap/empty (heap/merge-pairs comparator (cdr heap)))) ;; #+END_SRC
** Remote REPL
NB. REPL is currently disabled as sockets library doesn't work on M1. To enable it back uncomment ~(repl:start-repl-server)~ in ~ad-libitum-init~.
We need own repl server because music doesn't work in geiser repl for somewhat reason. The most universal solution would be to have REPL over either UDP or TCP with the simplest possible protocol. We want it to be just a carrier, everything else should happen inside editor and engine. Sadly Chez Scheme has no sockets in its std lib. We are gonna try Aaron W. Hsu's [[https://github.com/arcfide/chez-sockets][chez-sockets]] library.
Actually, we are still able to use Geiser with our REPL server because it supports remote REPL. See "Connecting to an external Scheme" at [[http://www.nongnu.org/geiser/geiser_3.html#The-REPL][docs]]. The only thing required for it is to load =scheme/chez/geiser/geiser.ss= into the REPL thread.
First, let's create a TCP socket. Here we rely on assumption, that default protocol is TCP.
*** TODO Ensure that protocol is TCP
*** Blocking vs Async sockets
Though Aaron doesn't recommend using blocking sockets, they are so much
easier for our case! No need to implement polling when waiting for
connection or receiving value.
Tried blocking sockets. They work fine by themselves, but play bad with
=sleep= called from other threads! Falling back to async sockets and polling
then.
*** Open socket
#+NAME: open-socket
#+BEGIN_SRC scheme
;;
Then we are going to listen address and port for input. We'll make it
configurable later, let's provide some sensible hardcoded defaults for now.
/localhost/ is for security reasons, and /37146/ is default Geiser port.
#+NAME: bind-socket
#+BEGIN_SRC scheme
;;
And then let's listen for new connections!
#+NAME: listen-socket
#+BEGIN_SRC scheme
;;
*** Accept connections
To actually accept new connections we are going to create new thread and
just run infinite loop with =accept-socket= inside. Remember, our socket is
non-blocking so we are to make polling to not eat all CPU by eager calls.
After accepting new connection we'll proceed it in new thread.
#+NAME: accept-connections
#+BEGIN_SRC scheme
;;
*** Spawn remote REPL
Every new connection accepted would spawn new thread with a REPL loop inside
it. Because we are using async sockets, we are forced to run actual loop and
poll socket for values. /50ms/ should be a reasonable polling delay to keep
it responsive and not resource greedy at the same time. Also
=receive-from-socket= require to limit maximum message length. Here /65k/ is
also is a kind of a guess. Chez Scheme operates UTF-8 strings and messages
are read as bytevectors from sockets, thus we need a transcoder to convert
them back and forth. Let's put all these requirements to values:
#+NAME: spawn-remote-repl-options
#+BEGIN_SRC scheme
;;
Preparations are straightforward: define some helpers, send initial prompt,
and start loop.
#+NAME: spawn-remote-repl
#+BEGIN_SRC scheme
;;
Converting messages to bytevectors and sending to proper port is quite
tedious, let's write a couple of helpers:
#+NAME: repl-send-helpers
#+BEGIN_SRC scheme
;;
Loop starts with polling delay. For simplicity it's constant and
unconditional in the beginning of every cycle. If socket is ready and
contains non-empty message then we do evaluation and send result back.
Reading from socket is implemented via ports, look at =chez-socket=
documentation for more info.
#+NAME: repl-loop
#+BEGIN_SRC scheme
;;
Our remote REPL supports multi-form messages, therefore we need inner loop to
read and process them one by one.
#+NAME: repl-read-eval-print
#+BEGIN_SRC scheme
;;
Eval and send result back, easy, huh?
#+NAME: repl-eval-print
#+BEGIN_SRC scheme
;;
Tricky part is that we want to:
- capture output performed by evaluated form
- capture result of form evaluated
- don't blow up on exception and capture its message
That's why we can't just call =eval=
#+NAME: repl-eval
#+BEGIN_SRC scheme
;;
On the other hand, sending is quite straightforward, because we need just to
write to port provided by =call-with-send-port=
#+NAME: repl-print
#+BEGIN_SRC scheme
;;
*** TODO Stop loop and close socket on disconnect
*** Start REPL server
#+NAME: start-repl-server
#+BEGIN_SRC scheme
;;
-
Core
Woohoo! Naive [[Kernel]] draft is here and we could start to explore Core basics of Sound. At this point Ad Libitum splits into into interwinded parts: the framework and the book. In the framework we are going to grow all necessary instruments for live coding. In the book we are going to use those instruments to experiment with sound.
One of the naming principles of Ad Libitum variables and functions is that they should have proper long self-describing name for clarity and could have any funky alias for shortening during performance and for fun cryptic librettos.
** Math
Before diving into the abyss of digital music let's define several useful basic math constants and functions.
#+NAME: basic-math
#+BEGIN_SRC scheme
;;
(define (random-amplitude) (- (random 2.0) 1.0))
(define (clamp value start end) (cond [(< value start) start] [(> value end) end] [else value])) ;; #+END_SRC
** Generators
Sound is about motion. About our mean of sensing somewhat periodic motion a.k.a waves. The higher is period, the higher is signal pitch. Waveform determines character of signal. And irregularities determine... Something. Noise? Personality? We'll try to discover.
Though signal demonstration usually started with sine waveform as the most recognizable and surprisingly pleasant one, we are going to start with computationally simplest one (though potentially not the fastest to calculate).
Technically, the simplest generator is just a constant value, no motion, silence. But which stands next in simplicity?
It's the signal, which is in one position half of a time and in another position in another half. By "time" here I mean one cycle, one period of signal.
But first let define a couple of constants to start with. It's a frequency we want to hear and its derivatives.
#+NAME: tuner-constants
#+BEGIN_SRC scheme
;;
#+NAME: simplest-oscillator
#+BEGIN_SRC scheme
;;
Actually, this waveform is called square, because of shape. Once we'll add visualisation library to Ad Libitum, before that try to draw function plot by hands.
Feel free to experiment with different waveforms, we will do it together later. Let's step back and look at our example and try to come up with useful abstraction. Our DSP callback has signature =f(time, channel) -> amplitude=, which is the basis for any audio signal. But what prevents us using audio signals as the main medium for building sound? Nothing! It's even very handy. Audio signals then are capable of control parameters of other signal, naturally forming audio graph. And Chez Scheme should optimize that CSP-like style well. But we need to think carefully ahead of time about signature itself. What if later we want add additional information flowing every sample? What if returning just float is not enough to express all we want? Because it's very beautiful, that every signal could be either interpreted as a DSP callback alone, and could be passed to other signals. But in the latter case sometimes it's not enough to communicate between signals with a single float. Perhaps something like =f(time, channel, data) -> (amplitude, data)= could do the job? Where structure of =data= is determined by your application, and parent signal is responsible for using or discarding the =data= returned by child signal. OTOH, =data= in parameters plays like a container for some global state to survive between samples, and we could replace it with actual global or closured state in our application. The same thing for returned data.
Let's start with =f(time, channel) -> amplitude= then and pray that we didn't overlook something important.
To ease writing signal creators and spotting them in code let's introduce small helper:
#+NAME: signal
#+BEGIN_SRC scheme
;;
(alias ~< signal)
(define-syntax (define-signal stx) (syntax-case stx () [(k args body ...) (with-syntax ([time (datum->syntax #'k 'time)] [channel (datum->syntax #'k 'channel)]) #'(define args (λ (time channel) body ...)))]))
(alias define~ define-signal) ;; #+END_SRC
Usage of that syntax sugar is highly encouraged as it eases refactor in case of arguments change, e.g. adding sample from audio input.
The most basic signal is just a constant one, which is essentially created by our shiny new syntax =(~< amplitude)=. But =~<= is a macro and having function is useful for composition matters:
#+NAME: constant
#+BEGIN_SRC scheme
;;
Then we are able to define =silence= as follows:
#+NAME: silence
#+BEGIN_SRC scheme
;;
Quick question for self-test: what sound would =(~< 1.0)= produce?
Though it's still very useful signal, let give it a separate name:
#+NAME: unit #+BEGIN_SRC scheme (define~ unit 1.0) #+END_SRC
Another useful syntax sugar is for referrign and setting vector element corresponding to the current channel. It is very common pattern to store signal state in vector on per-channel basis.
#+NAME: channel
#+BEGIN_SRC scheme
;;
(define-syntax (channel-ref stx) (syntax-case stx () [(k name) (with-syntax ([channel (datum->syntax #'k 'channel)]) #'(vector-ref name channel))]))
(define-syntax (channel-set! stx) (syntax-case stx () [(k name value) (with-syntax ([channel (datum->syntax #'k 'channel)]) #'(vector-set! name channel value))])) ;; #+END_SRC
For composing signal creators we could define a helper, which is the regular function composition!
#+NAME: compose
#+BEGIN_SRC scheme
;;
(alias ∘ compose) ;; #+END_SRC
For unifying oscillators we are going to define signal which will care about converting time to proper phase. When you deal with periodic signals it's important to distinguish time from phase, because at different frequencies phase would be different at the given point of time. Which is okay when frequency of you oscillator is constant. When it's variable as in FM synthesis, you need to track phase for your oscillator to make it behave properly. Let's create special signal =phasor= for that purpose. It will take =frequency= signal and =phase0= signal and return signal of phase in =[0, 1)= half-interval.
Here we have an opportunity for a small syntactic improvement. The use-case when signal is applied to parameters named exactly =time= and =channel= in current scope is very common. Let's create a special syntax for it.
#+NAME: deref-signal #+BEGIN_SRC scheme (define-syntax (<~ stx) (syntax-case stx () [(k signal) (with-syntax ([time (datum->syntax #'k 'time)] [channel (datum->syntax #'k 'channel)]) #'(signal time channel))])) #+END_SRC
There is a need trick to increase performance w/o breaching abstraction. If you have composite signal which you are sure produces same samples for every channel then you can build composite signal as usual, but wrap it in =mono= in the end to reduce load.
#+NAME: mono
#+BEGIN_SRC scheme
;;
Let's use it in our phasor signal. Phasor is used so frequently that we want to provide a small optimization for the case when frequency is known to be constant.
Note that =dynamic-phasor= relies on being called sample by sample. Skipping samples is okay-ish (it's like pausing phasor), but calling the same phasor from several other signals could make it move too fast. We need additional check to protect it.
#+NAME: phasor
#+BEGIN_SRC scheme
;;
(define~ (static-phasor frequency phase0) (-> time (* frequency) (+ phase0) (mod 1.0)))
(define phasor (case-lambda [(frequency phase0) (if (number? frequency) (static-phasor frequency phase0) (dynamic-phasor frequency phase0))] [(frequency) (if (number? frequency) (static-phasor frequency 0.0) (dynamic-phasor frequency ∅))]))
(alias /// phasor) ;; #+END_SRC
Then basic waveforms are defined in very clean way:
#+NAME: waveforms
#+BEGIN_SRC scheme
;;
(define~ (cosine phase) (cos (* 2π (<~ phase))))
(define~ (square phase) (if (< (<~ phase) 0.5) 1.0 -1.0))
;; when pulse-width' is (constant 0.5)' it's identical to `square-wave'
(define~ (pulse pulse-width phase)
(if (< (<~ phase) (<~ pulse-width))
1.0
-1.0))
(define~ (tri phase) (let ([phase (<~ phase)]) (if (< phase 0.5) (- (* 4.0 phase) 1.0) (+ (* -4.0 phase) 3.0))))
(define~ (saw phase) (- (* 2.0 (<~ phase)) 1.0))
(define (sampler table phase) (let* ([N (vector-length (vector-ref table 0))] [N-1 (- N 1)] [n (fixnum->flonum N)]) (~< (let ([position (* n (<~ phase))]) (let ([i (-> position (fltruncate) (flonum->fixnum) (clamp 0 N-1))] [a (mod position 1.0)] [table (channel-ref table)]) (+ (* (- 1.0 a) (vector-ref table i)) (* a (vector-ref table (mod (+ i 1) N)))))))))
(define (unroll signal base-frequency) (let* ([n (-> sample-rate (/ base-frequency) (round) (exact))] [table (make-channel-vector)]) (do-ec (: channel channels) (channel-set! table (make-vector n))) ;; channel is in inner loop because many `signal' functions ;; rely on ordered sample-by-sample execution (do-ec (: sample n) (: channel channels) (vector-set! (channel-ref table) sample (signal (/ sample sample-rate) channel))) table))
(define sine/// (∘ sine phasor)) (define cosine/// (∘ cosine phasor)) (define square/// (∘ square phasor)) (define pulse/// (case-lambda [(pulse-width frequency phase0) (pulse pulse-width (phasor frequency phase0))] [(pulse-width frequency) (pulse pulse-width (phasor frequency ∅))])) (define tri/// (∘ tri phasor)) (define saw/// (∘ saw phasor)) (define sampler/// (case-lambda [(table frequency) (sampler table (phasor frequency))] [(table frequency phase0) (sampler table (phasor frequency phase0))])) ;; #+END_SRC
Before we play something interesting with stuff we already defined we need one more helper. Drawback of our way of composition of signals is that we can't change code of one of them in live and make changed reloaded live, even if signal is not anonymous and was defined as a top-level variable. For signal which we plan to reload dynamically we are going to introduce wrapper which will look for given signal's symbol on every invocation:
#+NAME: live-signal
#+BEGIN_SRC scheme
;;
Also useful to have live value counterpart:
#+NAME: live-value
#+BEGIN_SRC scheme
;;
Next step is implementation of signal arithmetics to ease their mixing and matching.
#+NAME: signal-operators
#+BEGIN_SRC scheme
;;
(define (signal-sum x . xs) (fold-left signal-sum* x xs))
(define~ (signal-prod* x y) (* (<~ x) (<~ y)))
(define (signal-prod x . xs) (fold-left signal-prod* x xs))
(define (signal-diff x . xs) (let ([y (apply signal-sum xs)]) (~< (- (<~ x) (<~ y)))))
(define (signal-div x . xs) (let ([y (apply signal-prod xs)]) (~< (/ (<~ x) (<~ y)))))
(alias +~ signal-sum) (alias *~ signal-prod) (alias -~ signal-diff) (alias /~ signal-div)
(define ∑ (cut apply signal-sum <...>))
(define ∏ (cut apply signal-prod <...>))
;; normalizing +~ (define (mix . args) (*~ (∑ args) (constant (inexact (/ (sqrt (length args)))))))
(define~ (pan p) (let ([p (* 0.5 (+ 1.0 (<~ p)))]) (if (zero? channel) (- 1.0 p) p)))
(define~ (phase->interval phase start end) (let ([phase (<~ phase)] [start (<~ start)] [end (<~ end)]) (+ start (* phase (- end start)))))
(define~ (amplitude->phase s) (* 0.5 (+ 1.0 (<~ s)))) ;; #+END_SRC
** Envelopes
*** ADSR
ADSR envelope shapes signal with polyline described with 4 parameters:
- Attack time is the time taken for initial run-up of level from nil to peak, beginning when the key is first pressed.
- Decay time is the time taken for the subsequent run down from the attack level to the designated sustain level.
- Sustain level is the level during the main sequence of the sound's duration, until the key is released.
- Release time is the time taken for the level to decay from the sustain level to zero after the key is released.
(Thanks, [[https://en.wikipedia.org/wiki/Synthesizer#Attack_Decay_Sustain_Release_.28ADSR.29_envelope][Wikipedia]])
Two more parameter required to apply envelope in real performance: note's moments of start and end. To make envelope generic and open for crazy experiments all 6 parameters are going to be signals:
#+NAME: adsr
#+BEGIN_SRC scheme
;;
Let's test it with simple note play:
#+NAME: play-note
#+BEGIN_SRC scheme
;;
(define (make-play-note start end frequency) (λ (freq dur) (set-top-level-value! frequency freq) (set-top-level-value! start (now)) (set-top-level-value! end (+ (now) dur))))
;; (define start 0.0) ;; (define end 1.0) ;; (define frequency 440.0)
;; (define inst (simple-intrument 'start 'end 'frequency 0.3 0.5 0.8 1.0)) ;; (define play-note (make-play-note 'start 'end 'frequency))
;; (sound:set-dsp! (live-signal 'inst)) ;; (play-note 440.0 1.1) ;; #+END_SRC
We return to instrument concept later and come up with better design for it.
*** Impulse
Another simple though useful envelope is impulse.
#+NAME: impulse
#+BEGIN_SRC scheme
;;
*** Transition
#+NAME: transition
#+BEGIN_SRC scheme
;;
(define (instant-curve a Δx) Δx)
(define (linear-curve a Δx) (* a Δx))
(define (quadratic-curve a Δx) (* (expt a 4.0) Δx))
(define instant-transition (cut transition instant-curve unit <>)) (define linear-transition (cut transition linear-curve <> <>)) (define quadratic-transition (cut transition quadratic-curve <> <>)) ;; #+END_SRC
** Metronome
Metronome is a mean to align scheduling with some periodic beat.
#+NAME: beat
#+BEGIN_SRC scheme
;;
(define (beat->time beat bpm) (-> beat (* 60) (/ bpm)))
(define (next-beat time bpm) (beat->time (+ 1 (time->beat time bpm)) bpm))
(define (metro bpm . args) (apply schedule (next-beat (now) bpm) args))
(define bpm 60.0)
(define (set-bpm! bpm) (set! bpm bpm))
(define (beat) (time->beat (now) bpm))
(define (metro . args) (apply metro bpm args)) ;; #+END_SRC
** Control signals
#+NAME: control-signal
#+BEGIN_SRC scheme
;;
(define-syntax (define-control stx) (define construct-name (lambda (template-identifier . args) (datum->syntax template-identifier (string->symbol (apply string-append (map (lambda (x) (if (string? x) x (symbol->string (syntax->datum x)))) args)))))) (syntax-case stx () [(_ name initial-value) (with-syntax ([s (construct-name #'name #'name '~)] [ref (construct-name #'name #'name '-ref)] [set (construct-name #'name #'name '-set!)]) #'(begin (define-values (s name) (make-control initial-value)) (define (ref) (unbox name)) (define (set value) (set-box! name value))))])) ;; #+END_SRC
Hand by hand with control signal go various measurements. For them
signal-proxy =window= is very useful. It's result also could be used as the
input table for =osc:sampler=.
#+NAME: window
#+BEGIN_SRC scheme
;;
- Std
** FFT ** Filters
#+NAME: delay
#+BEGIN_SRC scheme
;;
#+NAME: echo
#+BEGIN_SRC scheme
;;
(define (make-echo max-line-duration) (λ (delay feedback signal) (let ([line-size (* max-line-duration sample-rate)] [lines (make-channel-vector)] [cursor -1]) (do ([channel 0 (+ channel 1)]) ((= channel channels) 0) (channel-set! lines (make-vector line-size 0.0))) (~< (when(zero? channel) (set! cursor (mod (+ cursor 1) line-size))) (let ([line (channel-ref lines)] [x (<~ signal)] [delay (flonum->fixnum (round (* (<~ delay) sample-rate)))] [feedback (<~ feedback)]) (let* ([i (mod (+ line-size (- cursor delay)) line-size)] [y (vector-ref line i)] [z (+ x (* feedback y))]) (vector-set! line cursor z) z))))))
(define echo (make-echo max-line-duration-fast)) (define echo* (make-echo max-line-duration-slow)) ;; #+END_SRC
#+NAME: lpf
#+BEGIN_SRC scheme
;;
(define (lpf frequency x) (let ([ys (make-channel-vector 0.0)]) (~< (let* ([y-1 (channel-ref ys)] [α (lpf-frequency->α (<~ frequency))]) (let ([y (+ y-1 (* α (- (<~ x) y-1)))]) (channel-set! ys y) y))))) ;; #+END_SRC
#+NAME: hpf
#+BEGIN_SRC scheme
;;
(define (hpf frequency x) (let ([xs (make-channel-vector 0.0)] [ys (make-channel-vector 0.0)]) (~< (let ([x-1 (channel-ref xs)] [y-1 (channel-ref ys)] [x (<~ x)] [α (hpf-frequency->α (<~ frequency))]) (let ([y (* α (+ y-1 (- x x-1)))]) (channel-set! xs x) (channel-set! ys y) y))))) ;; #+END_SRC
#+NAME: make-biquad-filter
#+BEGIN_SRC scheme
;;
#+NAME: biquad-lpf
#+BEGIN_SRC scheme
;;
(define biquad-lpf (make-biquad-filter make-lpf-coefficients)) ;; #+END_SRC
#+NAME: biquad-hpf
#+BEGIN_SRC scheme
;;
(define biquad-hpf (make-biquad-filter make-hpf-coefficients)) ;; #+END_SRC
** Instruments
#+NAME: polyphony
#+BEGIN_SRC scheme
;;
(define (make-static-polyphony n make-voice) ;; (make-voice) -> (list signal play-note) (let ([voices (list-ec (: i n) (make-voice))] [cursor 0]) (let ([signal (apply mix (map first voices))] [play-note (λ args (apply (second (vector-ref voices cursor)) args) (set! cursor (mod (+ cursor 1) n)))]) (values signal play-note)))) ;; #+END_SRC
** Scales
We are going to represent scales with Scheme's basic data structure, list. And the most basic operation which we want to perform on scale is chosing a note from it without worrying about falling out of range:
#+NAME: choice
#+BEGIN_SRC scheme
;;
(define (random-choice list) (list-ref list (random (length list)))) ;; #+END_SRC
Basic intervals from Western music.
#+NAME: intervals
#+BEGIN_SRC scheme
;;
(define second-interval (expt chromatic-scale-half-step 2)) (define third-interval (expt chromatic-scale-half-step 4)) (define perfect-fourth-interval (expt chromatic-scale-half-step 5)) (define perfect-fifth-interval (expt chromatic-scale-half-step 7)) (define major-sixth-interval (expt chromatic-scale-half-step 9)) (define major-seventh-interval (expt chromatic-scale-half-step 11)) (define perfect-octave-interval (expt chromatic-scale-half-step 12)) (define minor-second-interval (expt chromatic-scale-half-step 1)) (define minor-third-interval (expt chromatic-scale-half-step 3)) (define minor-sixth-interval (expt chromatic-scale-half-step 8)) (define minor-seventh-interval (expt chromatic-scale-half-step 11)) (define triton-interval (expt chromatic-scale-half-step 11)) ;; #+END_SRC
Some basic scales from Western music.
#+NAME: scales
#+BEGIN_SRC scheme
;;
(define (make-scale base-frequency scale) (map (λ (x) (* base-frequency (expt chromatic-scale-half-step (- x 1)))) scale)) ;; #+END_SRC
** Rhythm
#+NAME: pattern
#+BEGIN_SRC scheme
;;
** MIDI
#+NAME: midi
#+BEGIN_SRC scheme
;;
(define (on-note-off timestamp data1 data2 channel) (printf "~s:~s:~s:~s\r\n" timestamp data1 data2 channel))
(define (on-cc timestamp data1 data2 channel) (printf "~s:~s:~s:~s\r\n" timestamp data1 data2 channel))
(define (set-note-on! f) (set! on-note-on f)) (define (set-note-off! f) (set! on-note-off f)) (define (set-cc! f) (set! on-cc f))
(define polling-cycle 0.005)
(define stream #f) (define scheduler #f)
(define (process-event timestamp type data1 data2 channel) (cond [(= type pm:midi-note-on) (on-note-on timestamp data1 data2 channel)] [(= type pm:midi-note-off) (on-note-off timestamp data1 data2 channel)] [(= type pm:midi-cc) (on-cc timestamp data1 data2 channel)] [else (printf "Unsupported event type: ~s\r\n" type)]))
(define (make-safe-process-event timestamp) (lambda args (guard (_ [else #f]) (apply process-event timestamp args))))
(define (process-events) (let ([timestamp (scheduler:now scheduler)]) (when (pm:poll stream) (pm:read stream (make-safe-process-event timestamp))) (scheduler:schedule scheduler (+ timestamp polling-cycle) process-events)))
(define (start now) (unless stream (pm:init) (set! stream (pm:open-input 0)) (set! scheduler (scheduler:simple-scheduler now)) (scheduler:start-scheduler scheduler) (process-events)))
(define (stop) (when stream (scheduler:stop-scheduler scheduler) (pm:close stream) (pm:terminate) (set! stream #f) (set! scheduler #f))) ;; #+END_SRC
-
Misc
To import =chez-soundio= and =chez-sockets= we must add respective folders to =library-directories= To do that let's create a couple of helpers:
#+NAME: add-library-directories
#+BEGIN_SRC scheme
;;
(define (add-library-directories . dirs) (unless (null? dirs) (add-library-directory (car dirs)) (apply add-library-directories (cdr dirs))))
(add-library-directories "./chez-soundio" "./chez-portmidi" "./chez-sockets") ;; #+END_SRC
Also let's define several useful aliases and finally start our services:
#+NAME: ad-libitum-init
#+BEGIN_SRC scheme
;;
;; in case of emergency ☺ (alias hush! sound:hush!) (alias h! hush!)
(alias play! sound:set-dsp!)
(sound:start) (scheduler:init now) (scheduler:start) ;; (repl:start-repl-server) ;; #+END_SRC
Tuner stuff to test everything is working:
#+NAME: test-tuner
#+BEGIN_SRC scheme
;;
(define (quick-test signal) (signal (random 1.0) (random channels)))
;; (sound:set-dsp! tuner) ;; #+END_SRC
Some useful conversions, see TTEM.org for more details.
#+NAME: unit-conversion #+BEGIN_SRC scheme (define (amp->dB x) (* 20.0 (log x 10.0)))
(define (dB->amp x) (expt 10.0 (/ x 20.0)))
(define (midi-pitch->frequency m) (* 440.0 (expt 2.0 (/ (- m 69.0) 12.0))))
(define (frequency->midi-pitch f) (+ 69 (exact (round (* 12.0 (log (/ f 440.0) 2.0)))))) #+END_SRC
Some stuff about time and scales to be moved to appropriate sections when we'll come to them:
#+NAME: sandbox
#+BEGIN_SRC scheme
;;
(define (fix-duration duration) (let* ([start (now)] [end (+ start duration)]) (values (~< start) (~< end)))) ;; #+END_SRC
- Files :noexport:
#+NAME: ad-libitum.ss
#+BEGIN_SRC scheme :tangle ad-libitum.ss :noweb yes :mkdirp yes :paddle no
<
(import (ad-libitum common))
(voodoo)
(import (chezscheme) (srfi s1 lists) (srfi s26 cut) (srfi s42 eager-comprehensions) (ad-libitum signal) (prefix (ad-libitum control) ctrl:) (prefix (ad-libitum oscillator) osc:) (prefix (ad-libitum envelope) env:) (prefix (ad-libitum filter) filter:) (prefix (ad-libitum scale) scale:) (prefix (ad-libitum instrument) inst:) (ad-libitum metro) (prefix (ad-libitum noise) noise:) (prefix (ad-libitum sound) sound:) (prefix (ad-libitum scheduler) scheduler:) (prefix (ad-libitum repl) repl:) (prefix (ad-libitum midi) midi:) )
<
#+NAME: common.ss #+BEGIN_SRC scheme :tangle ad-libitum/common.ss :noweb yes :mkdirp yes :paddle no #!chezscheme (library (ad-libitum common (1)) (export voodoo λ id >>> >> -> ->> compose ∘ pi two-pi π 2π clamp choice random-choice random-amplitude amp->dB dB->amp midi-pitch->frequency frequency->midi-pitch channels sample-rate sample-angular-period) (import (chezscheme) (only (srfi s1 lists) reduce) (srfi s26 cut) (prefix (ad-libitum sound) sound:))
(alias *sample-rate* sound:*sample-rate*)
(alias *channels* sound:*channels*)
(define (voodoo)
(collect-maximum-generation 6)
(collect-generation-radix 2)
;; (eval-when (compile) (optimize-level 3))
(optimize-level 2)
)
;; symbols
(alias λ lambda)
;; can't live without
(define (id x) x)
<<compose>>
<<basic-math>>
<<unit-conversion>>
<<choice>>
(define *sample-angular-period* (/ 2π *sample-rate*))
;; threading
(define-syntax (>>> stx)
(syntax-case stx ()
[(_ it x) #'x]
[(_ it x (y ...) rest ...)
#'(let ([it x])
(>>> it (y ...) rest ...))]))
(define-syntax (>> stx)
(syntax-case stx ()
[(k rest ...)
(with-syntax ([^ (datum->syntax #'k '^)])
#'(>>> ^ rest ...))]))
(define-syntax ->
(syntax-rules ()
[(_ x) x]
[(_ x (y z ...) rest ...)
(-> (y x z ...) rest ...)]))
(define-syntax ->>
(syntax-rules ()
[(_ x) x]
[(_ x (y ...) rest ...)
(->> (y ... x) rest ...)])))
#+END_SRC
#+NAME: signal.ss
#+BEGIN_SRC scheme :tangle ad-libitum/signal.ss :noweb yes :mkdirp yes :paddle no
#!chezscheme
(library (ad-libitum signal (1))
(export signal ~< <~ define-signal define~
make-channel-vector channel-ref channel-set!
constant silence ∅ unit
mono
live-signal live-value
signal-sum signal-prod signal-diff signal-div
+~ *~ -~ /~ ∑ ∏ mix pan phase->interval amplitude->phase)
(import (chezscheme)
(srfi s26 cut)
(ad-libitum common))
<
#+NAME: oscillator.ss #+BEGIN_SRC scheme :tangle ad-libitum/oscillator.ss :noweb yes :mkdirp yes :paddle no #!chezscheme (library (ad-libitum oscillator (1)) (export phasor /// sine cosine square pulse tri saw sampler unroll sine/// cosine/// square/// pulse/// tri/// saw/// sampler/// ) (import (chezscheme) (srfi s42 eager-comprehensions) (ad-libitum common) (ad-libitum signal))
<<phasor>>
<<waveforms>>
)
#+END_SRC
#+NAME: noise.ss #+BEGIN_SRC scheme :tangle ad-libitum/noise.ss :noweb yes :mkdirp yes :paddle no (library (ad-libitum noise (1)) (export white) (import (chezscheme) (ad-libitum common) (ad-libitum signal))
(define~ white (random-amplitude))
)
#+END_SRC
#+NAME: envelope.ss
#+BEGIN_SRC scheme :tangle ad-libitum/envelope.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum envelope (1))
(export adsr impulse
transition instant-transition linear-transition quadratic-transition
)
(import (chezscheme)
(srfi s26 cut)
(ad-libitum common)
(ad-libitum signal)
(only (ad-libitum sound) now)
)
<
#+NAME: scale.ss
#+BEGIN_SRC scheme :tangle ad-libitum/scale.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum scale (1))
(export chromatic-scale-half-step
second-interval
third-interval
perfect-fourth-interval
perfect-fifth-interval
major-sixth-interval
major-seventh-interval
perfect-octave-interval
minor-second-interval
minor-third-interval
minor-second-interval
triton-interval
chromatic-scale
pentatonic-scale
major-scale
minor-scale
make-scale
)
(import (chezscheme)
(ad-libitum common))
<
#+NAME: control.ss
#+BEGIN_SRC scheme :tangle ad-libitum/control.ss :noweb yes :mkdirp yes :paddle no
#!chezscheme
(library (ad-libitum control (1))
(export make-control define-control window)
(import (chezscheme)
(srfi s42 eager-comprehensions)
(ad-libitum common)
(ad-libitum signal)
)
<
#+NAME: instrument.ss
#+BEGIN_SRC scheme :tangle ad-libitum/instrument.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum instrument (1))
(export make-polyphony)
(import (chezscheme)
(only (srfi s1 lists) first second)
(srfi s42 eager-comprehensions)
(ad-libitum common)
(ad-libitum signal))
<
#+NAME: filter.ss
#+BEGIN_SRC scheme :tangle ad-libitum/filter.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum filter (1))
(export delay
echo echo*
lpf
hpf
biquad-lpf
biquad-hpf)
(import (except (chezscheme) delay)
(ad-libitum common)
(ad-libitum signal))
<
#+NAME: metro.ss
#+BEGIN_SRC scheme :tangle ad-libitum/metro.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum metro (1))
(export metro metro beat play-pattern time->beat beat->time set-bpm!)
(import (chezscheme)
(ad-libitum common)
(only (ad-libitum sound) now)
(rename (only (ad-libitum scheduler) schedule)
(schedule schedule)))
<
#+NAME: sound.ss
#+BEGIN_SRC scheme :tangle ad-libitum/sound.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum sound (1))
(export start stop set-dsp! hush! sample-rate channels now)
(import (chezscheme) (prefix (soundio) soundio:))
<
#+NAME: scheduler.ss
#+BEGIN_SRC scheme :tangle ad-libitum/scheduler.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum scheduler (1))
(export start stop init
start-scheduler stop-scheduler schedule now
simple-scheduler
schedule now)
(import (chezscheme)
(only (soundio) usleep))
<
#+BEGIN_SRC scheme :tangle ad-libitum/repl.ss :noweb yes :mkdirp yes :paddle no
(library (ad-libitum repl (1))
(export start-repl-server)
(import (chezscheme)
(only (soundio) usleep)
(prefix (bsd-sockets) sock:))
<
#+NAME: violet.ss #+BEGIN_SRC scheme :tangle violet.ss :noweb yes :mkdirp yes :paddle no (load "ad-libitum.ss")
<
#+NAME: midi.ss
#+BEGIN_SRC scheme :tangle ad-libitum/midi.ss :noweb yes :paddle no
(library (ad-libitum midi (1))
(export start stop set-note-on! set-note-off! set-cc!)
(import (chezscheme)
(prefix (ad-libitum scheduler) scheduler:)
(prefix (portmidi) pm:))
<
** Tests
#+NAME: test-runner.ss #+BEGIN_SRC scheme :tangle ad-libitum/test-runner.ss :noweb yes :mkdirp yes :paddle no (import (chezscheme) (srfi s42 eager-comprehensions) (srfi s64 testing) (ad-libitum common) (ad-libitum signal) )
(define (test-on-test-end-simple runner) (let ((log (test-runner-aux-value runner)) (kind (test-result-ref runner 'result-kind))) (if (memq kind '(fail xpass)) (let* ((results (test-result-alist runner)) (source-file (assq 'source-file results)) (source-line (assq 'source-line results)) (test-name (assq 'test-name results)) (expected-value (assq 'expected-value results)) (actual-value (assq 'actual-value results)) ) (if (or source-file source-line) (begin (if source-file (display (cdr source-file))) (display ":") (if source-line (display (cdr source-line))) (display ": "))) (display (if (eq? kind 'xpass) "XPASS" "FAIL")) (if test-name (begin (display " ") (display (cdr test-name)))) (newline) (printf "Expected: ~s\r\nActual: ~s\r\n" (cdr expected-value) (cdr actual-value)))) (if (output-port? log) (begin (display "Test end:" log) (newline log) (let loop ((list (test-result-alist runner))) (if (pair? list) (let ((pair (car list))) ;; Write out properties not written out by on-test-begin. (if (not (memq (car pair) '(test-name source-file source-line source-form))) (%test-write-result1 pair log)) (loop (cdr list)))))))))
(define (my-test-runner) (let ((runner (test-runner-simple))) (test-runner-reset runner) ;; (test-runner-on-group-begin! runner test-on-group-begin-simple) ;; (test-runner-on-group-end! runner test-on-group-end-simple) ;; (test-runner-on-final! runner test-on-final-simple) ;; (test-runner-on-test-begin! runner test-on-test-begin-simple) (test-runner-on-test-end! runner test-on-test-end-simple) ;; (test-runner-on-bad-count! runner test-on-bad-count-simple) ;; (test-runner-on-bad-end-name! runner test-on-bad-end-name-simple) runner))
(test-runner-current (my-test-runner)) #+END_SRC
#+NAME: test-oscillator.ss #+BEGIN_SRC scheme :tangle ad-libitum/test-oscillator.ss :noweb yes :mkdirp yes :paddle no (import (ad-libitum oscillator))
(load "ad-libitum/test-runner.ss")
(test-group "phasor"
(let ([phase0 (~< 0.25)] [antiphase0 (~< 0.75)]) (do-ec (:real-range frequency 0.0 440.0 1.23456) (:real-range time 0.0 1.0 0.001) (: channel 2) (test-approximate "antiphase" 0.0 (+ ((sine (phasor (~< frequency) phase0)) time channel) ((sine (phasor (~< frequency) antiphase0)) time channel)) 1e-14)))) #+END_SRC
ul