I dont understand who subs work. Do substitutions have to be in key? What are the rules or norms associated with them?
substitutions are when one chord is substituted for another based on the similarity of the notes in each.

For example CMaj has notes C, E, G. Amin has notes A, C, E. The notes that they have in common are C and E. This is generally enough to substitute.

Some common substitutions are usually with the fourth and sixth diatonic chord of the scale, with an added 7th.
For Example CMaj7 (CEGB) could be substituted with FMaj7 (FACE) or Amin7 (ACEG)

Another way of substituting chords is Tritone Substitution. Where you substitute the chord based on an equal tritone.
I'll leave that research to you. As I think the first way of substitution is enough for you to get your head around. :P
Last edited by mdwallin at Sep 7, 2009,