Tip Of My Tongue

So I remember this old animation video I saw maybe early 2000s? About a couple of musicians, I think a guy and a girl, and they're chasing some sort...of music sphere? That gives them the inspiration to their music? Something like that...And as they follow hints to find it, they go traveling thorough rural america. I remember at some point they go on a cargo train wagon. I don't think it helps with timeframe reference, but I watched this video on some CD included on a magazine, and it was next to On Your Mark, which is widely more famous.