Interestingly the music.lua script in MAX appears to be empty, you could try copying over the one from GG to see if it all works.
Basically you specify the length of the sample when you load it like this:
music_load( 1, "audiobank\\Batman\\BatwingAudio\\BatwingMusicAudio.ogg", 0, 575712 )
The first parameter is the track number, the second number is the fade in time and the last parameter is total track length, both values are in milliseconds.
Then to set it playing:
music_play( 1 )
By default if the player dies the music will stop, to disable this use:
DisableMusicReset( 1 )
I've attached music.lua just in case you don't already have it.
It's possible it won't work if they haven't integrated these functions yet or if they have been disabled in MAX for some reason.
There are all sorts of useful functions in music.lua if it does work in MAX!
Been there, done that, got all the T-Shirts!