Re: Add Modal transformations (issue4126042)

[k-ohara5a5a]

This works very nicely for me.
One tiny oops, and suggestions you can take or leave as you wish.

I think I understand the point that some scales *can* un-ambiguously
named, but a facility to generate scales from these names is not
necessary for this patch.

I can type
 myPentatonic = \relative c' { a b d e fis }
just as easily as
 myPentatnoic = \majorPentatonicScale d



http://codereview.appspot.com/4126042/diff/5002/Documentation/notation/pitches.itely
File Documentation/notation/pitches.itely (right):

http://codereview.appspot.com/4126042/diff/5002/Documentation/notation/pitches.itely#newcode867
Documentation/notation/pitches.itely:867: pentatonicScale = \relative c'
{ ges aes bes des ees ges }
Oops, you want only the first /five/ pitches.
If you like, you could simplify by basing the scale on f
 \relative c' { f g a c d }
\motif = \relative c' { d8 c f,4 <f' a,> <f a,> }

http://codereview.appspot.com/4126042/diff/5002/Documentation/notation/pitches.itely#newcode943
Documentation/notation/pitches.itely:943: motif = \relative c' { c8.
ees16 fis8. a16 b8. gis16 f8. d16 }
Optionally, you could throw in a slur or crescendo or some other
spanner.  Users might otherwise assume the retrograding will break slurs
and do un-necessary work to put slurs in another variable.

http://codereview.appspot.com/4126042/diff/5002/Documentation/notation/pitches.itely#newcode967
Documentation/notation/pitches.itely:967:
Optionally, a note that ties break, even though slurs work fine.
(Internally, ties are only attached to one note)
@knownissues
Manual ties inside @code{\retrograde} will be broken and
generate warnings.  @ref{Automatic note splitting} can be
enabled to generate some ties automatically.

http://codereview.appspot.com/4126042/diff/5002/ly/music-functions-init.ly
File ly/music-functions-init.ly (right):

http://codereview.appspot.com/4126042/diff/5002/ly/music-functions-init.ly#newcode465
ly/music-functions-init.ly:465: modalInversion =
Since it is an operator, should it be a verb, modalInvert ?
The distinction between \transpose and \transposition is so tricky, that
I think it worth being careful in similar items.
\modalTranspose is the right name because it is an operation as is
\transpose

http://codereview.appspot.com/4126042/diff/5002/scm/modal-transforms.scm
File scm/modal-transforms.scm (right):

http://codereview.appspot.com/4126042/diff/5002/scm/modal-transforms.scm#newcode157
scm/modal-transforms.scm:157: ;; 5 octaves from the original scale
definition.  In practice there
It's not even that bad. If the scale is defined near middle C, we can go
from five-ish octaves below middle C to five-ish octaves above.  If I
move the scale away from my music I get the "pitch not in scale"
message, which I think is very reasonable.

http://codereview.appspot.com/4126042/