[Zubersoft]

Are you talking about playing back the MIDI as audio or streaming it to a connected device? I already support playing back MIDI files as audio (as the Android audio player supports this), so no changes are needed there. If you mean streaming the MIDI data in the file to a connected device, using an intent to launch an external application to handle the MIDI file wouldn't work very well I don't think. That application would have to ask for permission to access the MIDI device (and you might have to pick it from a list), and while you are doing that, you can't just play your score in MobileSheets. If that application loses focus, it may stop streaming the data (most applications won't just do this in the background if they are suspended). You can already try this out by using a smart button to link to the MIDI file. If you tap the button to load the file, it will ask what application to use (unless you've specified a default, in which case that one will be used). 

Mike