Isn't the data that comes from a midi controller typically already in the form of noteon/noteoff events? I know when I was messing around with an Akai MPD16 (drumpad thingy) I was getting note-ons coming out of it. There was no real "conversion" necessary, though I filtered out some things it was sending which I wasn't interested in. Maybe I misunderstand your question -- and I'm amateur, so don't take what I say as being authoritative by any stretch. Maybe you mean record incoming MIDI events into a MIDI format file? There's arecordmidi