shift-rhythm Function

Hello, Opusmoders

Sometime ago I was here searching for a function to displace rhtyhms by a length amount, not just like a list rotation.

Now I did this prototype. I think that this can be very useful, specially inside counterpoint dictums where patterns can be displaced ( I did not tried inside the counterpoint function but seems like it will work).

Hope it can be useful to you too.

All the best,

Julio

(defun shift-rhythm (rhythm shift-length &key span)

;"Moves rhythmic material by inserting a pause at the beginning.

;Use length-adjust to ensure the result fits within the span."

(let* ((rhy (flatten rhythm))

;;;; Ensures a linear list for processing

;; Adds the offset value as a negative pause at the beginning [5]

(with-offset (append (list (- (abs shift-length))) rhy))

;;Define the target span: either the requested one or the original rhythm.

(target-span (or span (get-span rhythm))))

;; The length-adjust function adjusts the total to the desired span [1].

;; With :position 'e (default), it removes or adds from the end of the list [6].

(length-adjust target-span with-offset :omn t :type 'r)))

;;; USE

;Exemplo 1: Span de 4/4 (1/1)

(setf ideia '(e c5 e d4 q f4 -h)) ;; Span original de 1/1

(shift-rhythm ideia 1/8 :span 3/4)

;; (-e e c5 d4 q f4 -e)

(shift-rhythm ideia 3/8 :span 5/4)

;; (-q. e c5 d4 q f4 -q.)

also with negative displacement

(setf ideia '(-h e c5 e d4 q f4 -h))

(shift-rhythm ideia -1/8 :span 7/4)

;;(-e -h e c5 d4 q f4 -h -e)

It could be perfected to deal with nested sublists and with different displacements for each sublist, like

(setf ideia '((-h e c5 e d4 q f4 -h)(-h e c5 e d4 q f4 -h.)(-h e c5 e d4 q f4 -q))

(shift-rhythm ideia '((-1/8) (2/16) (3/8)) :span 7/4)

etc