USB pedalboard in action - O God our Help in Ages Past

Learn to Play Sacred Music for all organs Book 1 by Meredith Barrett
(seems to be out of print and not very available - maybe I can reprint it?)

Bass Pedal Encoders at MIDI Kits:
https://midikits.net/products/bass_pedal_encoders/bass_pedal_encoders.htm

Aeolus:
https://kokkinizita.linuxaudio.org/linuxaudio/aeolus/