/ 
Music-Guidonian-0.01
River stage one • 1 direct dependent • 1 total dependent
/ Music::Guidonian

NAME

Music::Guidonian - a "Guidonian Hand" melodic phrase generator

SYNOPSIS

my $mg = Music::Guidonian->new(
  key_set => {
    intervals => [ 2, 2, 1, 2, 2, 2, 1 ],
    keys      => [qw(a e i o u)],         
    min       => 48,
    max       => 72
  }
);

my @text   = qw(Lo rem ip sum do lor sit);
my @vowels = map { m/([aeiou])/; $1 } @text;

my $iter   = $mg->iterator(\@vowels);

$iter->();        # [71,67,69,72,71,71,69] (maybe)

DESCRIPTION

"Guido of Arezzo" is credited with the creation of the "Guidonian Hand" which grew into among other things a method to aid with the creation of new music. This implementation is based off of a description of the process found in "Musimathics" (Volume 1, Chapter 9). In brief, pitches in a given ambitus are mapped to particular letters, usually vowels using some sequence of intervals (a scale). Then, given a sequence of those particular letters, a sequence of pitch numbers is returned for each call to an iterator function until no more possibilities remain, or, more likely for longer phrases, the caller gives up having found something suitable or otherwise having aborted early. Pitch numbers may be included in the input sequence to lock those positions to the given pitches.

Pitches are integers, typically MIDI numbers. These may need to be confined to a particular range (the ambitus) of values. Keys could be any scalar value but typically will be the vowels of a text phrase that is to be set to music. The caller may need to manually or otherwise process the text phrase to extract the vowels, and then after obtaining results from the iterator convert the pitch numbers returned into MIDI or musical notes for a scorewriter.

What is that synopsis code even doing?

The synopsis code should result in the keys (vowels) being mapped to pitches as follows;

 a  e  i  o  u  a  e  i  o  u  a  e  i  o  u
48 50 52 53 55 57 59 60 62 64 65 67 69 71 72
 C  D  E  F  G  A  B  C  D  E  F  G  A  B  C

the iterator function works (eventually, and assuming no bugs) through all possible combinations given that there are multiple choices for each vowel: the "o" of "Lorem" maps to 53 or 62 or 71, and then the "e", etc. Obviously longer phrases will suffer from what has been called the "combinatorial explosion" (see "The Lighthill debate on Artificial Intelligence").

Caveat

Various calls will throw exceptions when something is awry with the input.

Caveat

Various calls may accept bad data that will not generate known exceptions.

CONSTRUCTOR

The new method requires either that the key2pitch attribute is set, or that key_set containing intervals, keys, min, and max is set so that key2pitch can be constructed from those values.

Music::Scales can be used to obtain suitable intervals for different known scales. These will need to be converted with the intervalize_scale_nums function. Music::AtonalUtil is another way to obtain pitch set intervals.

ATTRIBUTES

key2pitch

This attribute must be set for the iterator method to be able to generate choices from a given sequence of keys. Example keys for a Latin phrase would typically be the vowels a e i o u. These vowels must map to one or more integer pitch numbers.

Music::Guidonian->new(
  key2pitch => { i => [60, 67], a => [62, 69], ... } );
);

METHODS

iterator sequence

This method accepts an array reference that is a sequence of key values or integer pitch numbers. A function is returned. Each call of the function will return an array reference containing a list of integer pitch numbers. When there are no more combinations an empty array reference is returned.

FUNCTIONS

These are not exported by default. They are mostly for internal use.

intervalize_scale_nums scale [ max-interval ]

Converts the output of get_scale_nums of Music::Scales into an interval form usable by this module.

use Music::Guidonian 'intervalize_scale_nums';
use Music::Scales 'get_scale_nums';
...
  intervals => intervalize_scale_nums([get_scale_nums('major')])
_previous_pitch

Internal. Looks up the previous pitch for a given pitch in a sequence.

_weight_choices

Internal. Orders the choices such that pitches closest to the previous pitch are returned first, as is common in melodic lines.

BUILD

Internal. This is a Moo utility function used by the "CONSTRUCTOR".

BUGS

None known.

SEE ALSO

MIDI, Music::AtonalUtil, Music::Scales, Music::VoiceGen

"Musimathics: the mathematical foundations of music". Gareth Loy. Mit Press. 2011.

COPYRIGHT AND LICENSE

Copyright 2021 Jeremy Mates

This program is distributed under the (Revised) BSD License: https://opensource.org/licenses/BSD-3-Clause