Well you can do what you want, there's nothing stopping you throwing a cheeky chord in which does not necessarily belong to the key you're working in. Music theory is a framework, but it's not a set of rules - at least that's what I keep telling myself Major key chord sequence (i, ii, iii, iv, v, vi, vii) : maj min min maj maj min dim Natural minor key chord sequence (i, ii, iii, iv, v, vi, vii) : min dim maj min min maj maj C major key - C, Dm, Em, F, G, Am, Bdim A minor key - Am, Bdim, C, Dm, Em, F, G C - F - G still belongs in the A minor scale, but you'll have moved position in the scale. In the major scale, C - F - G is i - iv - v. In A minor, if you're keeping the chords the same, you're playing iii - vi - vii. In A minor, the i - iv - v progression would be Am - Dm - Em. I find this site very useful for telling me which chords I should be using for a particular key: http://www.guitar-chords.org.uk/chordskey.html Hope that helps, and I hope I got it right!