[bewareandaware]

I thought they were all in the same key! I got mine because someone gave it to me. Then later I gave it to someone.

[nhumrich]

they come in the different transposed keys for instruments that read in different keys, but technically. the actual key, is all the same.

[ganafagol]

And the good jazz musicians can play their instrument from the C version. Over time you learn to transpose on the fly. It's just 12 keys after all, and the melodies tend to be not that complicated anyway.