MIDI Module Unit (Audio Unit) is General MIDI (GM) - MIDI Channel Selection
This video merely demonstrates, how to access the 16 MIDI channels of our MIDI Module Unit with the AUM host.
Obviously many of the latest users are grown with single timbre technologies. They do not even know what a multi-timbre synthesizer is, how to use or how to access the 16 MIDI channels.
Traditionally (in fact since MIDI exists), tone generators were made to play on 16 channels at ones with different timbres. You must switch to the correct MIDI channel, if you want to get all 16 channels. Drums are usually always on channel 10. Otherwise, a playback of MIDI arrangements would be impossible.
Lately, fundamental technologies were extremely simplified to merely use 1 channel / 1 timbre devices. (i.e.Audio Unit synthesizers and VST plugins are usually made this way) Unfortunately!
This is a reduction, a degradation in progress.
This is also inefficiently like hell.
Multi-timbre workstations are made for fast composing and creating the base of a song, the arrangement. You may polish the result with the single channel paradigm later.