traverse -package:base-compat -package:case-insensitive package:reactive-midyim

traverse :: (C msg, C msg) => msg -> State [Program] (Maybe msg)
reactive-midyim Reactive.Banana.MIDI.Program
Before every note switch to another instrument according to a list of programs given as state of the State monad. I do not know how to handle multiple channels in a reasonable way. Currently I just switch the instrument independent from the channel, and send the program switch to the same channel as the beginning note.
traverse :: (MonadMoment m) => s -> (a -> State s b) -> Event a -> m (Event b, Behavior s)
reactive-midyim Reactive.Banana.MIDI.Utility
traverseSeek :: (C msg, C msg) => Int -> msg -> State [Program] (Maybe msg)
reactive-midyim Reactive.Banana.MIDI.Program
This function extends traverse. It reacts on external program changes by seeking an according program in the list. This way we can reset the pointer into the instrument list. However the search must be limited in order to prevent an infinite loop if we receive a program that is not contained in the list.