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preserving ties when querying omn :length

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For various reasons, I need to start with rhythms defined in one time signature and remap them. I'm having trouble doing this because of what happens to ties when you use omn :length (though I realize they are being collected under :articulation).


In this case, I'm taking bars of 4/4 regrouping into bars of 2/4.


(setf myr '(
            (s s -s s -e s s -s s -e t t t t s s)
            (e e_q -h)))

(setf tr (omn-to-time-signature myr '(2 4)))


Now I take the result of the above and assign it to a new variable ( this would be the same as (setf foo tr) ):

(setf foo '((s c4 c4 - c4 -e s c4 c4) (-s c4 -e t c4 c4 c4 c4 s s) (e c4 c4 tie q) (-h)))


As you can see, there is a tie in the third bar.


Now, how can I extract that rhythm so that I can apply to another set of pitches?


If I do the following, I no longer have the tie represented in the rhythm:

(omn :length foo)

;; results in 
;; ((1/16 1/16 -1/16 1/16 -1/8 1/16 1/16) (-1/16 1/16 -1/8 1/32 1/32 1/32 1/32 1/16 1/16) (1/8 1/8 1/4) (-1/2))
;; i.e., no tie in the third bar


Also, if I try to span the rhythm onto another set of pitches, I again get a result that is missing the tie:

(setf my-pitches '(c4 d4 e4))
(make-omn :length foo :pitch my-pitches)


What I'd really love is to get back a list of lengths that is like my original list, just regrouped in new time signatures. So, ideally something like:

(setf myr '(
            (s s -s s -e s s -s s -e t t t t s s)
            (e e_q -h)))

;; imaginary function
(regroup-to-two-four myr)

;;would result in the following:
;;  ((s s -s s -e s s)(-s s -e t t t t s s)(e e_q)(-h))


Finally, I should add that in a related problem, I need to extract the number of attacks in a bar after it has been regrouped. So, for this reason again, I need to figure out how to extract the rhythm while preserving ties and not re-attacking tied notes.


I'd very appreciate and thank you kindly for any assistance in doing this.


Thanks very much, Michael

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