The more I think about it, the more I like the idea of varying the game by changing the music.
The source material gives us the default assumption of "bubblegum rock." But every darn muscial genre I can think of gets better when you add, "...and they're cartoons, and they solve mysteries."
I mean, look at a neo-swing band like Royal Crown Revue. You just KNOW those guys solve mysteries.
Blues. Bluegrass. Bebop. Hip-Hop. Rockabilly. Zydeco. It's all good.
[The rockabilly band could have a hound dog mascot. And the zydeco band could have an alligator.]
This game would also combine brilliantly with some of the other Poly minigames:
Mecha Crusade --- Wouldn't "Voltron" be a lot cooler if he formed a giant plasma guitar and rocked out?
Omega World --- This one is obvious. Post-apocolyptic survivalists...and they have a band. And they solve mysteries.
Shadow Chasers --- At the end, when you pull off the fake werewolf's mask...it's a vampire!
V for Victory --- You're a swing combo on a USO tour, entertaining the troops, solvin' them mysteries, and foiling those kooky Nazis [who probably have a really bad polka band].
Thunderball Rally --- It's already been done! It's the Jerry Reed episodes of Scooby-Doo! Eastbound and down, load it up and truck it! And bring your Telecaster!