`chorus` creates invalid csound expressions

[zeuner]

chorus seems to be unusable (csound 6.17 backend). Example expression:

dacBy (setTrace <> setJack "cse" <> setRates 48000 128  <> setBufs 8192 8192) $ chorus 0.07 1.25 0.25 $ usaw 300

It leads to this error message:

writing 4096 sample blks of 64-bit floats to dac
SECTION 1:
ftable 2:
new alloc for instr 18:
INIT ERROR in instr 18 (opcode delayw) line 48: delayw: associated delayr not found
 from file /tmp/tmp.csd (1),	delayw	ar0	
	  B  0.000 - note deleted.  i18 had 1 init errors

The stereo version chory seems to work, e.g. like this:

dacBy (setTrace <> setJack "cse" <> setRates 48000 128  <> setBufs 8192 8192) $ chory 0.07 1.25 0.25 $ (\x -> (x, x)) $ usaw 300