[dduck]

I am not sure m4a format can be played on Android devices.

[honestcoyote]

Of course it can. m4p files are right out but those should be nearly extinct by now.

The player app on my phone plays just about every audio format available, including ogg and flac.

[mikeash]

Why wouldn't it? It's an open standard. Even if AAC decoding isn't built in, you could easily provide your own decoder for it.