*Muscript*
is a language for typesetting music.

This page describes the use of Variables,
as introduced in *muscript* 3.1.

This part of the syntax is still under development;
future backward-compatibility is not guaranteed.

Variable-names begin with a **$** like *Perl* variables.
Of the remainder,
the first character must be an upper-case A-Z,
and the rest upper-case letters or digits 0-9.
This makes the variable easy to spot within the text.
Some examples:

` $A $B6 $MIDDLE8 $RIFF1 $CODA`

$B4 = 8 [D G B'] $RIFF1 = 83 [E 163 e' G G# B 83 d' 163 B 83 A 163 B] 2 restThe variable-definition must have a line to itself. On the left hand side of the equation, the variable-name, as in

` $A = cycle? D# : F# : A ?`

$B = [$A $A]

=1 treble $B $B $B $B

evaluates to:` =1 treble [D# F#] [A D#] [F# A] [D# F#]`

If you want to force substitution here at definition-time,
use **==** a double equal-sign. So:

` $A = cycle? D# : F# : A ?`

evaluates to:

$B **==** [$A $A]

=1 treble $B $B $B $B

` =1 treble [D# F#] [D# F#] [D# F#] [D# F#]`

$B5 = { # comments starting with a # are allowed here | 4.3 =1 treble 4 G A B c =2 bass 8 rest 4 g e d 8 D }This allows whole sections of music to be stored in a variable. When substituted, they are considered not to start with a newline, but they are considered to finish with an inbuilt newline. Therefore whole pieces of music can be expressed on one line, e.g.:

$OPENING $VERSE $CHORUS $VERSE $CHORUS $MIDDLE8 $VERSE $CHORUS $CHORUS

If you want to force substitution here at definition-time,
use **==** a double equal-sign. This can lead to recursion:

$B5In this (absurd) example, the value of the $E8 and $F9 variables will only be set when $B5 is actually=={ | 4.3 $B==[$A $A] =1 4 G $B c $B =2 8 rest 4 g e d 8 D =1 $B $B $B $B $C6=={ $D7=={ $E8={ $F9=={ =1 1 $B } } } } $C6 | $E8 =1 4 G $B B c =2 8 rest 4 g e d 8 D }

To make changing the notes of a chord easier, a very restricted one-line syntax allows :

$B2-4 = G : Bb : dwhich is neater than the equivalent :

$B2 = G $B3 = Bb $B4 = dOnly single-digit suffixes are allowed.

Variables can be generated by one of a number of in-built functions:

**aaba**,
**cycle**,
**leibnitz**,
**morse_thue**,
**rabbit** and
**random**

These functions return one of their arguments each time they are invoked;
they get invoked every time the variable occurs in the text and is substituted.

` $B = rabbit? 8 [D G B'] : 8 [Eb G A] ?`

Think of the question-mark as introducing the question "

*which?*",
and think of the colon **:** as a field-separator,
like it is in */etc/passwd*.
(These characters are not otherwise used in *muscript* syntax.)

There must be no space between the function-name
and the first question-mark.

Spaces inside the question-marks, or next to the colons, are stripped away:
you can use them for clarity.

If you want a multi-line field, you have to
define a multiline variable,
then use that variable in the field.

**aaba**-
The Aaba sequence can be generated by starting with 0 0 1 0,
then repeatedly appending to it the same thing,
the inverse, and the same thing again.
It's reminiscent of the "Sentence" or a minimalised "Sonata-Form",
but it's fractal.
It needs just two arguments.
The first three stages are 0 0 1 0

then: 0 0 1 0 0 0 1 0 1 1 0 1 0 0 1 0

then:

0 0 1 0 0 0 1 0 1 1 0 1 0 0 1 0

0 0 1 0 0 0 1 0 1 1 0 1 0 0 1 0

1 1 0 1 1 1 0 1 0 0 1 0 1 1 0 1

0 0 1 0 0 0 1 0 1 1 0 1 0 0 1 0

In general, if you generate 4^{n}elements, the ratio of a/b is (2^{n}+ 1) / 2^{n}- 1), which tends towards 1.0 **cycle**- This function just generates its arguments cyclically, in a loop.
**leibnitz**-
The Leibnitz sequence with n=2 can be generated
by repeatedly appending the current sequence with one added to it.
The first five stages are 0, then 0 1, then 0 1 1 2,
then 0 1 1 2 1 2 2 3, then 0 1 1 2 1 2 2 3 1 2 2 3 2 3 3 4.

The Leibnitz sequence with n=3 can be generated by repeatedly appending the current sequence with one added to it and then with two added to it. The first four stages are 0, then 0 1 2, then 0 1 2 1 2 3 2 3 4, then 0 1 2 1 2 3 2 3 4 1 2 3 2 3 4 3 4 5 2 3 4 3 4 5 4 5 6.

Since it's necessary to specify**n**, this is done as the first argument. For example,

`$A = leibnitz? 2 : A : B : c : d : e ?`

=1 $A $A $A $A $A $A $A $A $A $A $A $A $A $A $A $A

results in:

`=1 A B B c B c c d B c c d c d d e`

**morse_thue**-
The Morse-Thue sequence is named in honour of
the Norwegian mathematician Axel Thue (1863-1922)
and of Marston Morse of Princeton (1892-1977).
It is now more commonly known as the Thue-Morse Sequence.

With 2 arguments, the sequence can be generated by repeatedly appending the complement; the first five stages are 0, then 0 1, then 0 1 1 0, then 0 1 1 0 1 0 0 1, then 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0.

With K=3 it can be generated by recursively by adding 1 and then 2, modulo 3. The first three stages are 0, then 0 1 2, then 0 1 2 1 2 0 2 0 1.

See: en.wikipedia.org/wiki/Thue-Morse_sequence **rabbit**-
The Rabbit sequence arises from Fibonacci's rabbit-problem
in the Liber Abaci (1202). It needs just two arguments.
The sequence can be generated by starting with the first two stages 1,
then 1 0, and then appending to each stage the previous stage;
so the next four stages are 1 0 1, then 1 0 1 1 0,
then 1 0 1 1 0 1 0 1, then 1 0 1 1 0 1 0 1 1 0 1 1 0.

See: en.wikipedia.org/wiki/Fibonacci_word **random**- The Random sequence always returns one of its elements at random.

When a variable is encountered within the music
(rather than just within a recursion in a
variable-definition),
then it is substituted,
and any new variables which appear as a result are themselves substituted,
and so on recursively until there are no variable-names left at all.
Then the pre-processing is complete, and the result is interpreted by
*muscript*.

muscript -pp filenameThis

See *alberti.txt*,
*fingerpickin.txt* and
*generators.txt* in
**samples/index.html**

**test.pl**,
the test-script that this version passes

**index.html**,
the *muscript* home page

**Fractals, Chaos, Power Laws**, Manfred Schroeder, 1991,
W.H. Freeman, New York

**
en.wikipedia.org/wiki/Thue-Morse_sequence**

**
en.wikipedia.org/wiki/Fibonacci_word**,
about the Rabbit Sequence.

*Peter Billam*
*http://www.pjb.com.au*