If you want to play with your DAW or just play some tunes using Fluidsynth, you will usually use a MIDI keyboard. But if all you have right now is your phone, you can still use USB MIDI output.
While this is a built-in Android feature, Xiaomi doesn’t show this option by default. Don’t worry though, the functionality is still enabled. All you need to do to switch to USB MIDI mode is to go to the Developer Settings menu on your phone and find USB Mode.
Don’t have developer settings enabled?
You can enable it by going to Settings, clicking “About Phone” and tapping the MIUI Version around 5-6 times.
After this step, under Settings - More Settings, you will have your Developer Settings.