Hi echolevel - thanks for your reply, I’ve been trying to get help with this on the unreal engine answers forum to no avail 
I’ve set up a simpler version - when the player enters a trigger box above the pink square, a timer starts the NoteOn through a custom event. If the Velocity variable is not connected and I enter a value manually, this works correctly - I can see the timer working and the note plays at 2 second intervals. When I connect the velocity variable the note appears to be playing (that is, the timer is looping and the string prints correctly, switching from 0 to 120 and back by pressing F) but I can’t hear anything… maybe could you post a shot of how you’ve implemented it?