Originally Posted by: Blkcrr939

So the chords of this song go [br][br]

C/G > Cmaj7/G > Am > F > Em

I thought the 1 chord would be C, but does having a G in the bass note change anything?

Thanks to jarkko for the great reply!

In order to find the key signature of any group of chords you identify all the notes in all the chords, then build a scale with them. That's the essence of key signature, the scale that all (or most) of the notes in a melody or chord progression belong to.

Notice that if you do that for all those chords, you could also be in A minor. Because C major & A minor are relative major & minor to each other. It could be either. Clearly stating a melody line could also help clarify the key signature.

I cover that process in depth in this tutorial.

https://www.guitartricks.com/tutorial.php?input=876

You might also find my tutorial on major scale harmony useful.

https://www.guitartricks.com/tutorial.php?input=2387

Hope that helps!