i was wondering the same... let me give everyone an example... if there is a just a Bb in the key signature.. is the piece in Fmajor? .. since there is a Bb in the Fmajor scale?
Originally posted by Leftover_Crack
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Emo is: "I had sex with your mom.. why hasn't she called?"
You mean if there's ONLY a Bb/A# note? It would fit into any key that uses the A#, but if that's the first note most likely it's an A# major or minor.

You determine the key of the song by what notes it uses. C major is C, D, E, F, G, A, B. No sharps.