Found under: Settings > MIDI > Custom MIDI commands
In addition to song MIDI messages, which are saved and loaded with a song, you can also assign custom MIDI commands to 8 user assignable MIDI actions. These actions can be assigned to foot pedals, page buttons or custom gestures.
A use of these buttons could be for a general 'start' MIDI message, to play a drum sound, or to change an effect setting on a sound processor, etc.
To edit a MIDI action, click on the button 1-8 and then click on the EDIT button. By default the buttons have been set up to send MIDI note on commands to play beats on a drum kit.
You will then be taken to the MIDI shorthand command builder and you can add as many messages as you like to this button (multiple messages get sent in order with the MIDI delay specified in the settings page between them).
You can then assign the MIDI action to a footpedal, page button or custom gesture. Of course, before the MIDI command can be sent via the action, you first need to connect to a MIDI device in OpenSongApp. These are listed from the commands as MIDI Action 1, Midi Action 2, etc..