I tried it a day ago and it was working as expected.  Today I think I'm losing it.  I have a drum synth with audio track and associated midi track.  I go to media browser and select a MIDI drum pattern.  I select "Draw Pattern" from "Draw" and get a paint roller cursor which can paint the MIDI pattern in the synth audio track, but no paint roller when I move to the MIDI track and I can't paint there.  Of course the MIDI pattern does nothing in the synth audio track.  What am I doing wrong?

OK, never mind - just had to be positioned in the lower half of the MIDI track.