2) Built in Objective-C with a custom audio engine in C++. Audio latency on Android was horrible at that time, MS was probably worse. It would have been a terrible app on those platforms if I did port it. This was before cross-platform toolkits existed. It needed to be a native app with low level access audio to hardware. I wasn't going to make an app where you tap a drum and wait 100ms to hear a sound.
Not that this counters anything you said nor that relevant to this topic, but as a nerd I am genuinely curious if this was true. I used to write lowlat audio stuff for iOS so I was well aware of the situation Android vs iOS (and because of my large interest in audio Android in general always makes me puke in my mouth a little -- like it is one of those neat little hidden indicators that while Apple is a hardware company, Google is fundamentally an ad company -- they really don't give a shit other than prioritizing ad delivery).
Anyway, Windows itself obviously has solid low-lat audio services, was it really that bad in the mobile stuff?