Re: MIDI sync
I think you can get it to work, just not everything at one time. This much I know for sure, MC6 will always be the master since it has no master/slave settings.
MC6 can read data from a midi controller and it can transmit midi to an external sound module. If midi echo is turned on then MC6 will receive midi and then re-transmit, or echo, whatever midi it receives.
First in MC6 set tempo and set up a midi track for MC6 to receive and record midi data from the TR-707. Record the midi data.
Return MC6 and the TR-707 to the start of the song.
Set a track in MC6 to record audio next and record the TR-707 audio.
Align the two tracks.