Control other synths, samplers, and apps with expressionPad.
CoreMIDI on your iOS Device
CoreMIDI lets you play synths and samplers in other apps from expressionPad.
The most important thing to remember is that your other audio app needs to have background audio enabled — because you’ll be playing expressionPad in the foreground, and you’ll want to hear the synth/sampler from the other app playing.
Sometimes this Background Audio option in the Settings app, under the entry for the relevant app. Sometimes it’s in the app itself.
Playing expressionPad with MIDI activated
Now, return to expressionPad and activate the MIDI panel.
Turn on MIDI OUT. Also, open up the SYNTH panel and turn down the volume — unless you want the synthesizer playing along with the audio app in the background.
The MIDI Session, “Session 1” should suffice for playing apps on your device. The other options are useful when you’re in more complicated audio setups.
MIDI Channel can be useful if you have multiple MIDI-enabled instruments in your other apps; specific instruments can have their own channels assigned.
Playing OSX audio apps with expressionPad
We’ll need MIDI OUT to be on, just like with CoreMIDI apps on iOS devices.
Open up the Audio MIDI Setup app on your computer.
Double-click the Network icon.
You should see your device listed. You can try connecting to that or you can hit the [+] button and enter in the IP address listed in the MIDI panel in expressionPad.
Finally, make sure your audio app like Garage Band, Reason, or Logic Pro X is open, select an instrument to play, and rock out with expressionPad!
There’s more advanced info on Audio MIDI Setup app at this Sound on Sound article