midichan
From TidalCycles userbase
Type: midichan :: Pattern Double -> ControlPattern
midichan turns a number pattern into a control pattern that controls what MIDI channel to play a MIDI pattern on.
midichan is indexed at zero, which means a value of "0" will play on MIDI channel 1, a value of "1" will play on MIDI channel 2, and so on.
d1 $ note "0 3 7 9" # s "midi" # midichan "5"
Observe that you can make a pattern to play on multiple MIDI channels:
d1 $ note "0 3 7 9" # s "midi" # midichan "5 1 0 3"