This took me a while to figure out, so I thought I'd share here.
My friend sent me a midi kick drum track, and I wanted to send it to my Arturia Drumbrute Impact and record the audio back into Reaper. Here's how that worked:
1.connect Arturia Drumbrute Impact to PC with USB cable
2.set up Reaper project - options - midi devices - output: Arturia Drumbrute Impact 'enabled'
3.create a track - 'Route' - Midi hardware output - select Arturia Drumbrute Impact
4.Import the midi track (don't tick the boxes). This needs to be on note 36 for kick, etc. up to 54. (see drum map attached)
5.Double-click on the take; this opens midi editor
6.On lower right corner, change 'All channels' to 'channel 10'
7.Click on C2 (key 36) for kick drum to test; should work
8.Edit - select all --> change notes to triangle pointing to the right with midi icon top bar.
9.While all notes still selected, right-click on one of the notes, select 'Note channel' and then 'channel 10'.
10.Press play; should work.
