It’s possible to control Reason Compact from other iOS music making apps that can send MIDI. To do this you can use an "audio and MIDI routing" app like the Audiobus 3.
In the example below we connect the Fugue Machine app that sends MIDI to Reason Compact, which acts as sound source:
1. Launch the Audiobus 3 app, tap the MIDI button at the bottom left and tap to select the MIDI Sender application - the Fugue Machine app:
2. Tap to select Reason Compact as the MIDI Receiver app:
3. Now, Reason Compact is set up and ready to be MIDI controlled by the Fugue Machine:
4. Switch to the Fugue Machine app and start playback, and Reason Compact will play along.
Note that you can only control one single instance ("track") of Reason Compact.