Chords In Keys

[Richard_close2u]

@Avidity

Wild Horses by The Rolling Stones is in the key of G major. When I looked at all the chords in that song, I saw that they matched the scale (G, Bm, C, D) except for two of them. Am and F are in that song, but those notes are not in the G major scale. Is that normal to sometimes play chords that are not in the key of a song?

Good question based on your learning Dave.

Note that Am and is extension Am11 are in the key of G (diatonic chords) so it is only F (Fadd9) that seems not to fit.

The G major scale and its diatonic triads (chords):

In the borrowed chord topic kindly linked by Kim above, Example 5 has a progression in the key of G major too, from where I can use the same partial Circle of Fifths.

Look at the parallel key of G minor to see that the F chord (extended in the song to Fadd9) is borrowed from the parallel minor key.

I hope that helps.