OK, first of all, I can't figure out how to get music on the debug 360 to test it out. But it sure looks like if you have some music on the HD, you'd be able to use it. I mean, right now, since my drive is basically empty, there is only "Default Playlist and Sample Playlist". But there are quite a few empty spaces underneath, making me lean to saying you can grab music off the hard drive. But again, I can't test it, unless I can figure out how to get music files on this thing.

For stadiums, you can select beats for solo homerun, 2-run homer, 3-run homer, grand slam, Top of inning over, end of game, between pitch(H) and (A), batter over, batter intro (H) and (A), single, double, triple, walk, action replays, home run derby, pause, pitcher intro (H) and (A), game intro and bottom of inning over.
For players, it claims when you set the beat for the batter, it overrides the songs in the stadium beats, again making it seem like you can pull music from the HD.
So, to put it bluntly... I don't know exactly what you can or can't do here. Sorry. But if I find a way to import music to this debug, I'll check back in.

Comment