Hey I'm trying to take a short recording I made a year ago and turn it into a full song, but can't figure out which key it should be in.

From what I can tell, I have a single not melody/intro thing that is based on the Bb pentatonic, and then there is a following chord progression that goes Gmaj -> Bbmaj -> Cmaj.

What key is this/should it be and what can I play to solo over it?
I've tried soloing in Bb maj and that kinda worked, even though Bb has Cmin and Gmin.
Also tried in G, which worked but didn't sound as well to my ears.

Anyway, I don't have the best ear and my music theory is shotty, so help me out UG.
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Depending on the style, I'd say you best bet is to play in G major most of the time. The Bb chord kind of throws a wrench in that, so, could switch to minor there for that chord, or use minor pentatonic, or Bb pentatonic.

If it's a fast rock and roll sort of riff, then, you're probably good with G minor pentatonic or G blues.
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It's in G, but you're using G minor for melodies and getting a bluesy sound. The clash between the major third (B) in the chord and the minor third (Bb) over it is called a Blue Note.

I'd suggest keeping E natural over that C maj, though. Depending how fast those chord changes are you might switch up your melodies over each one to get a jazzier sound, too.
Thanks for the responses, G works.

And cdgraves, when you say keep the E natural over the C maj, are you refering to when playing in G min?
It's Cadillac rainbows and lots of spaghetti
And I love meatballs so you better be ready