Virtual / Inter-app MIDI Connections

This requires Android 6 or larger with full MIDI support! (Sadly not all vendors consider it necessary to support MIDI)

Virtual / Inter-app MIDI connections are another new feature in Android 6. There is not all that much to say about it, the title basically says it all: You can exchange MIDI between apps with this approach and it remains to be seen what other developers make of it. TouchDAW itself does not offer any virtual ports, it will just let you connect to virtual ports offered by other apps or services. You could use the keyboard or pads to play synths for example.

Note that virtual devices that do not receive MIDI, but would only send MIDI to TouchDAW are ignored (because controlling a controller doesn't really make much sense).

To select a virtual connection, touch the port you want to change at Setup / MIDI Ports and select "Virtual" in the first dialog. (If you do not see such an option, it means that you do not have any other app that registered itself as a virtual MIDI destination installed.)

Offerings may still be sparse, but three years after this functionality was introduced to Android a number of synthesizer apps supporting it are indeed available on the Play Store. If you have any of them installed, another dialog as shown on the right will come up. Select the one you want, click OK and you're done as far as the TouchDAW side goes. Depending on how it is built, you may still need to actually launch the target app (ports will be visible no matter if the app is running or not) and select the port in question in that app.

Like all ports virtual device ports can only be opened by one app at a time outputwise.
It should also be noted that virtual ports occasionally fail to open on the first attempt. Restarting the app with the port selection in place will usually bring them up ok then.