12 tone issue

[JulioHerrlein]

Dear Friends,

 

I was revisiting some 12-tone theory today and I found something strange:

 

This returns NIL

 

(twelve-tonep '(c3 eb3 d3 f3 e3 g3 fs3 a3 gs3 b3 bb3 cs4))

 

but this returns TRUE

 

(twelve-tonep '(c4 eb4 d4 f4 e4 g4 fs4 a4 gs4 b4 bb4 cs4))

 

It´s the SAME tone-row

 

NIL for this

(twelve-tonep (pitch-transpose -12 '(c4 eb4 d4 f4 e4 g4 fs4 a4 gs4 b4 bb4 cs4)))

 

TRUE for this

 

(twelve-tonep (pitch-transpose 0 '(c4 eb4 d4 f4 e4 g4 fs4 a4 gs4 b4 bb4 cs4)))

 

Maybe the algorithm to find the row is based in the c4 octave...

 

I don´t know...

 

Best

 

[LdBeth]

Despite the documentation says Return true if sequence is a twelve-tone row, from what I observed it seems the algorithm used is:

 

(defun twleve-tone-p (omn)
  (equal (sort (pitch-to-integer omn) #'<) (range 0 11)))

 

[LdBeth]

I think you might want this:

(defun tw-p (omn)
  (equal (let ((x (sort (pitch-to-integer omn) #'<)))
           (x-b x (apply #'min x)))
         (range 0 11)))

 

And in you example it seems should be '(c3 eb3 d3 f3 e3 g3 fs3 a3 gs3 b3 bb3 cs3) instead of cs4.

 

(let ((x (pitch-to-integer '(c3 eb3 d3 f3 e3 g3 fs3 a3 gs3 b3 bb3 cs3))))
           (x-b x (apply #'min x)))

(0 3 2 5 4 7 6 9 8 11 10 13)

 

[opmo]

row is from 0 to 11 with 12 intervals.

what is the reason to do this:

 

(twelve-tonep (pitch-transpose -12 '(c4 eb4 d4 f4 e4 g4 fs4 a4 gs4 b4 bb4 cs4)))

 

[JulioHerrlein]

Dear Janusz,

 

Just for testing. When the octave changes, the function give wrong result.

I´m doing a workaround putting before an (ambitus-octave c4 1

 

Best,

Julio

Maybe it´s better to embed the ambitus constraint in the function or something similar in order to get right results in any octave.

Since the concept of "pitch class" is octave independent...

[opmo]

Quote

Just for testing. When the octave changes, the function give wrong result.

No wrong result, just wrong use of the function.

[JulioHerrlein]

Is this a  wrong use ?

 

(twelve-tonep '(c3 eb3 d3 f3 e3 g3 fs3 a3 gs3 b3 bb3 cs4))

 

 

why ?

[opmo]

Quote

Since the concept of "pitch class" is octave independent...

Use modus first and than the twelve-tonep

 

This is correct:

(twelve-tonep '(c3 eb3 d3 f3 e3 g3 fs3 a3 gs3 b3 bb3 cs4))
=> nil

 

is not 12 tone row.

 

With modus:

(twelve-tonep (modus '(c3 eb3 d3 f3 e3 g3 fs3 a3 gs3 b3 bb3 cs4)))
=> t

 

[JulioHerrlein]

Thanks. 

It have to be constrained in one octave.

 

 

I´ll remember to put modus before any octave independent use of tone-row.

[opmo]

This function is only for tests.

[JulioHerrlein]

Yes. Thank you.