There are a few steps involved to get to that goal.
First, as you may know, MIDI messages such as notes are sent on a single MIDI channel. Therefore you need to ensure that the Reface DX is transmitting MIDI notes on a channel that the OT is listening to. You also need to ensure that the OT knows that you want to play its sounds and not (yet) do anything else.
To set that up, you need to do the following:
On the OT:
- select the TRIG MODE “CHROMATIC”
- in the PROJECT > MIDI > CONTROL menu, set AUDIO NOTE IN to “FOLLOW TM”
- in the PROJECT > MIDI > CHANNELS menu, make a note of the value of AUTO CH (the default value is 9)
On the DX:
In the MIDI Settings screen, set the TR CH (MIDI Transmit channel) to match the number of the OT’s AUTO CH setting.
Now you should be able to find a two-octave range of the DX’s keyboard that will play whatever sound you have loaded on the active audio track of the OT. It will play monophonically (one note at a time) because the OT does not play polyphonically on a single audio track. Try this out and see what happens.
To get chords you would have to either:
- load a chord sample into the OT’s audio track, or
- use an external device to spread the notes you play on the DX keyboard to more than one audio track of the OT.