;; r = root
;; q = maj or minor
;; c = chord
;; where c can be symbol 'i7 or list '(0 3 7)
(define set-chord
(lambda (r q c)
(set! root r)
(set! chord (if (symbol? c) (pc:diatonic root q c) c))
(set! scale (pc:scale-from-chord root chord))))