diff options
| -rw-r--r-- | scales.scm | 83 |
1 files changed, 48 insertions, 35 deletions
@@ -1,6 +1,10 @@ -(use-modules (srfi srfi-1) - (srfi srfi-26)) +(define-module (scales) + #:use-module (ice-9 match) + #:use-module (srfi srfi-1) + #:use-module (srfi srfi-9) + #:use-module (srfi srfi-26)) + (define all-notes (circular-list 'a 'ais 'b 'c 'cis 'd 'dis 'e 'f 'fis 'g 'gis)) @@ -66,45 +70,54 @@ root note and returns a list of scale notes." '((c g d a e b) (c g d a e b))) -(define (steps->offsets steps) - "Given a list of semitone steps return a pattern of absolute -pitch offsets." - (reverse - (fold (lambda (step acc) - (cons (+ step (car acc)) acc)) - '(0) steps))) - -(define (scale->notes scale root) - (let ((notes (all-notes-from root))) - (map (lambda (offset) - (list-ref notes offset)) - (steps->offsets scale)))) - -(define (fretboard tuning notes frets fret-offset) - "Generate a fretboard (a list of lists of notes) for an instrument -with the given TUNING where the position of the given NOTES are -indicated for as many FRETS as specified." - (let ((keep-notes (lambda (note) - (if (member note notes) - note #f)))) - (map (lambda (root) - (map keep-notes - (drop (take (all-notes-from root) - (+ frets fret-offset)) - fret-offset))) - (reverse tuning)))) - -;; TODO: keep more metadata, e.g. scale position +(define-record-type <fret> + (make-fret position note) + fret? + (position fret-position) + (note fret-note)) + + + +(define* (string-frets root scale-notes + #:optional (frets 7) (fret-offset 0)) + "Represent an instrument string as a list of FRETS frets. Each fret +contains a <FRET> object holding its position (starting from +FRET-OFFSET) as well as the scale note matching one of the SCALE-NOTES +at this position or #f." + (map (match-lambda + ((position note) + (make-fret position + (find (lambda (scale-note) + (eqv? note + (scale-note-note scale-note))) + scale-notes)))) + (zip (iota frets fret-offset) + (take (all-notes-from root) + (+ frets fret-offset))))) + +(define* (fretboard tuning scale-notes + #:optional (frets 7) (fret-offset 0)) + "Generate a fretboard (a list of lists of frets) for an instrument +with the given TUNING where the position of the notes of a given SCALE +are indicated for as many FRETS as specified." + (map (lambda (root) + (string-frets root scale-notes frets fret-offset)) + (reverse tuning))) ;;; Printing +(define (print-fret fret) + (let ((note (fret-note fret))) + (format #t "-~3,,,'-,a-|" + (if note + (if (zero? (scale-note-offset note)) + (string-upcase (symbol->string (scale-note-note note))) + (scale-note-note note)) + "-")))) (define (print-frets frets) (display "|") - (for-each (lambda (note) - (format #t "-~3,,,'-,a-|" - (if note note "-"))) - frets) + (for-each print-fret frets) (format #t "\n")) (define (print-fretboard fretboard) |