dechord

[Cliff]

I have the following chord progression:

 

(setf chords '((w (c4 maj7))
               (w (a4 m7))
               (w (d4 m7))
               (w (g4 7))
               ;
               (w (c4 maj7))
               (h (a4 m7/b5))
               (h (a4 m7))
               (h (d4 m7/b5))
               (h (d4 m7))
               (w (g4 7))
               ))

 

When evaluating following expression on it ...

 

(dechord chords :pitch 'root)

 

... I get following result in the listener:

 

((w b4 mf) (w e5 mf) (w a4 mf) (w b4 mf) (w b4 mf) (h g5 mf) (h e5 mf) (h c5 mf) (h a4 mf) (w b4 mf))

 

I expected the roots.

Am I doing something wrong?

 

---

 

EDIT:

Just played around with the other keyword options...

:pitch 'low

... return the expected result. Still I am confused.

 

 

Can someone explain the result with :pitch ‘root ?

[opmo]

(pcs-normal-order (melodize 'c4e4g4b4))
=> (11 0 4 7)

 

Yes, the :pitch 'low will return the lowest pitch in the chord.

[Cliff]

Thx @opmo understood,

so keyword :root  is not really what is typically tought as chord root (if I exclude pcs theory).

:low seems to be the "new" root.

 

Feedback, even if pcs-theory-wise justified, OM-API is a bit counter-intuitive here in my humble users point of view.

At least I suggest to make an extra note in the documentation so that other do not fall into the same trap as I did.

Yes I know the existing example indicates this surprise already, but please add your pcs "justification", this will explain the rationale.

 

(dechord (chord-inversion 0 (expand-chord '(c4 maj7))) :pitch 'low)

-> ((c4))

 

and

 

(dechord (chord-inversion 1 (expand-chord '(c4 maj7))) :pitch 'low)

->  ((e4))

[opmo]

Addition and improvements to DECHORD function:

 

 

(setf chords '((w (c4 maj7))
               (w (a4 m7))
               (w (d4 m7))
               (w (g4 7))
               (w (c4 maj7))
               (h (a4 m7/b5))
               (h (a4 m7))
               (h (d4 m7/b5))
               (h (d4 m7))
               (w (g4 7))
               ))
               
(dechord chords)
=> ((w c4 mf) (w a4 mf) (w d4 mf) (w g4 mf) (w c4 mf) (h a4 mf) (h a4 mf) (h d4 mf) (h d4 mf) (w g4 mf))

(dechord chords :type 'pcs)
=> ((w b4 mf) (w e5 mf) (w a4 mf) (w b4 mf) (w b4 mf) (h g5 mf) (h e5 mf) (h c5 mf) (h a4 mf) (w b4 mf))

(dechord chords :pitch 3)
=> ((w g4 mf) (w e5 mf) (w a4 mf) (w d5 mf) (w g4 mf) (h ds5 mf) (h e5 mf) (h gs4 mf) (h a4 mf) (w d5 mf))

 

See the document for more explanation (3.0.29342).