Use the following procedure to change the MIDI channel and OMNI mode of the TR-626:
- Enter Track Play mode.
- Press the START/STOP button to stop the rhythm if it is running.
- While holding SHIFT, press SYNC/MIDI.
- While continuing to hold SHIFT, press ENTER until omn (Omni Mode), rch (receive channel) or tch (transmit channel) is displayed.
- Use the VALUE DIAL to change the desired setting.
Owner's Manual: https://www.roland.com/us/support/manual_archive/