Re: Include and document the Articulate script by Peter Chubb. (issue4277067)

[Peter Chubb]

Hi Francisco,
   If this is (finally!) going to get in, it'd be worth having
   somewhat better documentation than it has.  You've done a pretty
   good job of grabbing the stuff I had in my ReadME file, but if this
   is no longer to be a chunk of source code that's downloaded
   separately, (where one can reasonably assume that the downloader
   will read the comments in the file), but a tool to `just use', I'd
   suggest adding the following to the documentation.


-----

Articulate manipulates the lengths of notes to make them sound more
like a musician might play them.  
1. It changes notes to be non-legato, except under slurs or phrase
   marks. 
2. It notices slurs and phrasemarks, and makes all notes under them
   take their full value, so they play legato.
3. If notes are marked staccato, staccatissimo and tenuto it adjusts
   their lengths accordingly.
4. Tempo markings are observed.  However, in Lilypond most tempo marks
   are just text, so not all marks can be captured.  More can be added
   fairly easily.  The marks observed in version 1.6 are:
   * rall., Rall, rall, rit. --- slow the tempo by about 40%.
   * poco rit., poco rall. --- slow the tempo by about 10%
   * a tempo or tempo I --- return to the tempo before the last
   ritenuto.
   There is not any accelerando yet.
6. Trills, turns, pralls and mordents are expanded.  The baroque
   practice of staring on the auxiliary note is assumed for trills.
7. The common idiom, \afterGrace c\trill {b8 c}
   is noticed and the gruppetto adjusted to have the same timing as
   the trill.
8. \appogiatura is changed so that the grace note takes half the value
   of the principal note, or one third if the note is dotted,
   according to Baroque performance practice.

There are some parameters one can tweak to get the performance you
want.  In particular if you want the musc to be legato throughout, set
ac:normalFactor to '(1 . 1) --- this improves organ music and recorder
music when it is written without phrasing marks.



% PARAMETERS
% How much to compress notes marked Staccato. 
#(define ac:staccatoFactor '(1 . 2)) 

% How much to compress notes marked staccatissimo.
#(define ac:staccatissimoFactor '(1 . 4))

% And tenuto
#(define ac:tenutoFactor '(1 . 1))

% How much to articulate normal notes.  CPE Bach says 1/2 (and 
% staccato should be `as short as may conveniently be played') but this 
% sounds too short for modern music.  7/8 sounds about right.
#(define ac:normalFactor '(7 . 8))

% How much to slow down for a rall. or a poco rall.
% (or speed up for accel or poco accel)
#(define ac:rallFactor (ly:make-moment 60 100)) % 40% slowdown
#(define ac:pocoRallFactor (ly:make-moment 90 100)) % 10% slowdown

% The absolute time for a twiddle in a trill, in minutes.
% Start with 1/4 seconds == 1/240 minutes
% This is adjusted according to the tempo of the music, and the lenght
% of the note trilled.
#(define ac:maxTwiddleTime (ly:make-moment 1 240))


--
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
http://www.ertos.nicta.com.au           ERTOS within National ICT Australia