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Re: Transposition with arrow quarter-tone notation
From: |
Keith OHara |
Subject: |
Re: Transposition with arrow quarter-tone notation |
Date: |
Fri, 18 Feb 2011 23:46:38 -0800 |
User-agent: |
Opera Mail/11.01 (Win32) |
Joseph Wakeling wrote:
This setup is aimed allow for a full arrow quarter-tone notation with
arrows being preserved across all regular transpositions
Suppose we use arrow notation to represent some just-intonation scheme, in
which the 'up-arrow' alterations are some odd fraction :
NATURAL 0
NATURAL-RAISE 2/9
SHARP-LOWER 1/2 - 2/9
SHARP-RAISE 1/2 + 2/9
Transpositions can general a very large number of net alterations. We could
adapt the \naturalizeMusic function from the manual into something that
*rounds* the result to the nearest representable pitch (the function
\enharmonicReduce in the attached file).
The extra bit of code for to the tuning scheme above is :
(let ((o (ly:pitch-octave p))
(a (ly:pitch-alteration p))
(n (ly:pitch-notename p)))
[... the usual conversions like cisis to d ...]
;;
;; for use with arrowed alteration glyphs, defined only for
;; values of a that are +/-1/2, or +/-1/2 +/- 2/9
;;
(let ((semi (* (round (/ a 1/2)) 1/2)))
(set! a (+ semi (* (round (/ (- a semi) 2/9)) 2/9))))
(ly:make-pitch o n a)))
This rounding destroys information, so we apply it as the last operation before
printing.
\score {{
#(set-accidental-style 'dodecaphonic)
\time 3/2
\enharmonicReduce \transpose d beseh { \quartertonephrase }
}}
arrow2.ly
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arrow2.png
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