Keyboard players, guitar players, or any other musician that relies on MIDI gear often have to remember which part of a song needs which MIDI patch. This incurs mental overhead and makes it harder to perform your music live.
Using this app, you can create lists of songs, where parts of the song (such as verse, chorus, etc) transmit MIDI program change messages and other control parameters to your external MIDI gear. Use a page turner pedal or map any MIDI message to the next patch / previous patch buttons, and scroll through your patches when you perform your song without taking your hands off your guitar or keyboard.