Hi Leigh,I heard you can change 1 4 5 chords to Minor chords and then you can change 2 3 6 to Major Chords is this true? Here another example ,You can take 1 6 7 5 Chord progression turn into Heavy Metal or Hard Rock song,I notice Iron Maiden use lot of songs they have lot of 1 6 7 chord progression.I notice Dio Rainbow in Dark is 1 6 7 5 chord progression and I notice that lot in 70s music and specialty in 80s music they use 1 6 7 chord progression.Thank you,James