; replace non first 0s into 12
; facilitates turning a diatoninc pclass into a pitches list
(define helper:handle_zeros
(lambda (l)
(let ((a (car l)) (b (cadr l)) (c (caddr l)))
(if< b a (set! b (+ 12 b)))
(if< c b (set! c (+ 12 c)))
(list a b c)
)))