In this case, Footy has a trendy techno pulse track with bouyant 'Match of the Day' theme in the menu's and when managing your club. It's happy music, so there's a cowbell, as you'd expect. It's low and gentle mixed behind the bass and pulse...until you play it on a tablet. Then there's nothing but incessant *bing* *bing* *bing* as the cowbell completely overpowers everything else!
Not a problem - just turn it down in the mixer. But had I not listened to the music on the target device, I'd have driven my first few users insane with the audio. And if I'd commissioned some music, I may have been even less aware of the issue and in no position to do anything about it other (beyond pester the composer).
So all would-be mobile game composers out there, make sure you are listening on devices as you create, and appreciate how your audio range is so limited in the bottom end and overpowered in the mids when mixing. Maybe even create a master EQ to simulate the frequency range of a tiny speaker.