mask

Type: mask :: Pattern Bool -> Pattern a -> Pattern a

mask takes a boolean (aka binary) pattern and 'masks' another pattern with it. That is, events are only carried over if they match within a 'true' event in the binary pattern.

For example consider this kind of messy rhythm without any rests.

d1 $ sound (cat ["sn*8", "[cp*4 bd*4, hc*5]"]) # n (run 8)

If we apply a mask to it

d1 $ mask "t t t ~ t t ~ t"
  $ s (cat ["sn*8", "[cp*4 bd*4, bass*5]"])
  # n (run 8)

Due to the use of cat here, the same mask is first applied to "sn*8" and in the next cycle to "[cp4 bd4, hc*5]".

You could achieve the same effect by adding rests within the cat patterns, but mask allows you to do this more easily. It kind of keeps the rhythmic structure and you can change the used samples independently, e.g.

d1 $ mask "1 ~ 1 ~ 1 1 ~ 1"
  $ s (cat ["can*8", "[cp*4 sn*4, jvbass*16]"])
  # n (run 8)

See struct for more examples for dealing with binary patterns.