[flush] and [midiflush] will both sit in the midi stream and, when activated, end any notes which happen to be playing.
I don’t think that’s what Jesse’s asking for. It sounds like he wants to modify the contents of a MIDI clip, removing all notes from it.
No simple command for that; it’s a series of LOM calls. (getting the address of the current track, finding the currently playing clip, and editing its contents…)