MIDI options include:
Select the MIDI note that marks the split between left and right pads when using a MIDI device to tap double rhythms.
Select the MIDI note to use for hi hat, snare, and kick drum pads when using a MIDI device to tap drumkit rhythms.
Turn MIDI Send on or off. When MIDI Send is on, Rhythm Lab's internal sounds are ignored, and the sounds from MIDI apps or devices found on the iPad system will play instead.
Bluetooth MIDI - find Bluetooth MIDI devices within range of the iPad and select/turn on Bluetooth MIDI if it has not already been turned on by another app on the iPad.