I recently bought the sheet music to this song but don't understand the notation. The signature key has an F#, which I believe means the key of G. However there is a notation that states "Keyboard and Guitar A minor". When I play my guitar along with the song the guitar chords that are written sound correct. And when I start picking out the melody on a keyboard all the F#'s sound correct in the beginning but then everything seems to fall apart quickly. Can anyone explain to me what I am doing wrong with the keyboard? Thanks.