I play alto saxophone and my friend plays guitar. How do I transpose his chord c

Question:

I play alto saxophone and my friend plays guitar. How do I transpose his chord changes so I can jam with him?

What key is the guitar in? That might give me some idea of where to start.

Best Answer - Chosen by Asker: C. Almost all instruments except for the sax family (Eb Alto, Bb Tenor, Eb Bari) and the trumpet (Bb Trumpet, D Trumpet, etc) and Clarinet (Bb, Eb alto) etc., are in C. This includes all of the stringed instruments (the kind you strum and the kind you bow, except for the Ukelele, which you can tune to whatever key you want) percussion instruments, etc. This is a very broad overgeneralization, but hang with me.

You transpose by adding 3 sharps to the concert key, or by transposing down a minor third or up a major 6th. (Which is why when you play "concert Bb," which I'm guessing you've done, you play your G scale)

So...
Guitar = You
C = A
C# = Bb
D= B
Eb = C
E = C# (tough, because LOTS of guitar songs are in E)
F = D
F# = Eb
G = E
Ab = F
A = F# (tough, because LOTS of guitar songs are in A)
Bb = G
B = Ab