helper:pc_to_interval   scheme

;; turn a pitch class step interval notation to a more traditional interval notation
;; eg 
;; intervallo di 1 = same note VS 0 in pc steps
;; intervallo di 2 = next pitch in scale VS 1 in pc steps
;; intervallo di 4 = quarta eg 'fa' in do maggiore VS 3 in pc steps
;; intervallo di 8 = ottava VS 7 in pc steps
;
(define helper:pc_to_interval
  (lambda (pcstep)
    (cond	((> pcstep 0)
            (- pcstep 1))
          ((< pcstep 0)
            (+ pcstep 1))
          (else 0))
    )
)