Input level adjustment

[riban-bw]

It may be advantageous to add an input level control that can boost / antenuate the audio input. Pitch detection seems to be dependant on optimal audio level hence this control could be useful. I also observe that lower notes are detected more readily that higher notes, apparently due to signal level so some form of filter and/or compressor may be advantageous.

It would also be advantageous to have a signal output that indicates audio input level and some form of quality and/or trigger indication.