Here is the mysterious section from the manual:
PROG CH SEND will when checked send out program change MIDI messages when the active pattern on the Octatrack MKII changes. Which channel the messages are sent on is controlled by the setting below.
CHANNEL sets which channel the Octatrack MKII should send program change messages on. The LEVEL knob is used to change this setting. If AUTO is chosen the first MIDI channel used by the audio tracks, and not used by any of the MIDI tracks, will be used. If CHANNEL is set to a specific MIDI channel, that channel will be used to transmit program change messages.
Re-reading this now, I understand that they are talking about the “elektron” program messages only. It has nothing to do with PCMs from on the individual midi channels. Those are sent regardless of these settings - they’re sent even with “send” unchecked. I think my whole misunderstanding centered around this. I do wish the manual were somehow more clear about it.
Previously I had disabled all the audio midi channels in the MIDI CHANNELS page so that explains why I didn’t get “elektron” PCMs with the AUTO setting. Now I’m able to get PCMs on the channel assigned to the lowest numbered audio track in in the TRIG CH section of MIDI CHANNELS.
So AUTO means: use the channel assigned to the lowest numbered audio track that isn’t already assigned to a MIDI channel.
Why would anyone want to do that? How are the audio track’s midi channels related to “elektron” program change messages (other than this strange setting)?