Just make sure you get instrumental stuff. Most of the vocal tunes are cheesy songs about Pokémon and friendship. Trust me, I've looked.

[Some have catchy enough melodies, but there are only so many times he can take tunes like Pokémon world. In a way, lyrical songs make repetition even more apparent.]

And if you've gotta focus on the gyms, I guess there's no real rush. It might be better to start once you're finished, since it's not like they give us anything to do after the fact.