Pattern Bool -> Pattern a -> Pattern a -> Pattern a
stitch uses the first (binary) pattern to switch between the following two patterns. The resulting structure comes from the binary pattern, not the source patterns. This differs from sew where the resulting structure comes from the source patterns.
d1 $ stitch "1(8,16)" (cc "0:64") $ sound "midi"
This will use the boolean pattern to send CC0 with a value of 64 to midi.