Gramophone is an algorithmic generator of music composition.
gramophone2 [-c|-d] sourcefile [midifile]
-c
is an option allowing you to control the syntax of the source without generating music.
-d
is an option allowing you to activate debug mode, with video output of the composition and player parameters plus the generated notes.
In GRAMophone, the music is generated using two kinds of formal grammar: Chomsky's regular grammar (or Type 3) for a TOP DOWN approach to the composition and a reduced version of Lindenmayer grammar for a BOTTOM UP approach.
GRAMophone is partly based on an idea of Jon McCormack's, who invented the idea of a virtual player (virtual musician). The player in question is associated with a MIDI track, and interprets instructions telling it what to do. Generally, they say play notes (send MIDI messages). GRAMophone's players together make up an orchestra, which plays a composition.
Any number of players can play a composition, but in practice the hardware used might impose an upper limit.
In general every player plays an instrument and each has a different set of grammar rules. An individual player is characterised by a set of parameters which are shared by the whole orchestra and/or a personal parameter set.
The orchestra's parameters consist of:
the kind of grammar used (Chomsky or Lindenmayer);
the metronome;
the measure;
the number of iterations used in the production process.
Each individual player's parameters consist of:
the kind of grammar used (Chomsky or Lindenmayer);
the instrument;
the MIDI channel associated with the player;
the number of iterations used in the production process;
A player's notes have a current state consisting of:
octave
volume
duration
release
These characteristics can be controlled parametrically by a player declaring its associated variables. GRAMophone, then, allows for the non-deterministic generation of music, using either Chomsky or Lindenmayer grammar.
"Give Me A" (The "Hello, World!" for GRAMophone")
To introduce you to the basic ideas, here is the simplest algorithmic composition that can be generated with GRAMophone: this composition simply generates the note A and is presented through both the Chomsky and Lindenmayer methods.
composition "Give Me A" of "Schroeder" {
//this composition generates the A note with the Chomsky grammar
grammar chomsky
tempo 120
time_signature 4/4
%
player Schroeder {
instrument 0
%
@composition->A[,,,];
}
}
composition "Give Me A" of "Schroeder" {
//this composition generates the A note with the Lindenmayer grammar
grammar lindenmayer
tempo 120
time_signature 4/4
%
player Schroeder {
instrument 0
%
axiom->A[,,,];
}
}
THE KEYWORDS composition E of
All compositions must begin with the keyword composition followed by a string (in inverted commas) containing the name of the composition. This must be followed by the keyword of then another string containing the copyright of the piece.
THE COMPOSITION BLOCK
The composition block is placed in brackets. It is subdivided into three sections: one section defines parameters of the composition, one declares and initiates any global variables and an orchestra section where the players who will 'play' the piece are defined. The first two sections are separated by the % symbol.
THE player KEYWORD
Each player is defined with the keyword player, followed by an identifier.
THE player BLOCK
The player block is placed in brackets and is divided into three sections: one section defines the parameters of the track associated with the player, one declares any local variables for the player and one is for the formal rules. The first two sections are separated by the % symbol.
COMMENTS
In GRAMophone, comments are C-like: they must begin with the character pair '/*' and end with the character pair '*/.' There must be no space between the asterisk and the slash. Everything between these pairs of symbols will be ignored by the GRAMophone parser. Whole lines of comments may also be included. Lines of comments begin with the symbol // and end at the end of the line, as in the two initial examples.
Section defining the composition's parameters
The parameters shared by all the orchestra's players are declared here. The parameters that may be declared are:
grammar
resolution
iterations
tempo
time_signature
This section must end with the % symbol.
grammar
This parameter is obligatory and defines the kind of grammar to be used in the generation. This can be either chomsky or lindenmayer.
resolution
This parameter defines the number of time units of 1/4 duration. If omitted, the default value 480 will be used.
iterations
This parameter defines the number of iterations contained in the generation. Its meaning depends on the kind of grammar chosen, as explained below. If omitted, the default value 1 will be used.
tempo
This parameter defines the composition's rhythm. If omitted, the default value 120 will be used.
time_signature
This parameter defines the composition's measure. If omitted, the default value 4/4 will be used.
Section declaring the composition's global variables
The variables control the parameters of a note's attributes, as explained below.
Section defining the player's parameters
Each player's personal parameters and variables are declared here. The personal parameters that may be declared are:
instrument
channel
iterations
This section must end with the % symbol.
instrument
This parameter indicates the player's instrument type. GRAMophone's instrument set is the same as that of General MIDI. The acceptable range of values is 0 to 127; there are therefore 128 instruments to choose from. A table showing the instrument codes appears below:
0 Piano
1 Brite Piano
2 HammerPiano
3 Honkey Tonk
4 New Tines
5 Digital Piano
6 Harpsichord
7 Clavi
8 Celesta
9 Glocken
10 Music Box
11 Vibes
12 Marimba
13 Xylophon
14 Tubular Bell
15 Santur
16 Full Organ
17 Percussive Organ
18 BX-3 Organ
19 Church Organ
20 Positive
21 Musette
22 Harmonica
23 Tango
24 Classic Guitar
25 Acoustic Guitar
26 Jazz Guitar
27 Clean Guitar
28 Mute Guitar
29 Overdrive Guitar
30 Distorted Guitar
31 Harmonics
32 Jazz Bass
33 Deep Bass
34 Pick Bass
35 Fretless Bass
36 Slap Bass 1
37 Slap Bass 2
38 Syntethized Bass 1
39 Syntethized Bass 2
40 Violin
41 Viola
42 Cello
43 Contra Bass
44 Tremolo String
45 Pizzicato
46 Harp
47 Timpani
48 Marcato
49 Slow String
50 Analog Pad
51 String Pad
52 Choir
53 Doo Voice
54 Voices
55 Orchestra Hit
56 Trumpet
57 Trombone
58 Tuba
59 Mute Trumpet
60 French Horn
61 Brass Section
62 Synthetized Brass 1
63 Synthetized Brass 2
64 Soprano Sax
65 Alto Sax
66 Tenor Sax
67 Baritone Sax
68 Sweet Oboe
69 English Horn
70 Bassoon Oboe
71 Clarinet
72 Piccolo
73 Flute
74 Recorder
75 Pan Flute
76 Bottle
77 Shakhukuhachi
78 Whistle
79 Ocarina
80 Square Lead
81 Saw Lead
82 Caliope Lead
83 Chiff Lead
84 Charang Lead
85 Air Chorus
86 Rezzo4ths
87 Bass & Lead
88 Fantasia
89 Warm Pad
90 Poly Synth Pad
91 Ghost Pad
92 Bowed Pad
93 Metal Pad
94 Halo Pad
95 Sweep Pad
96 Ice Rain
97 Soundtrack
98 Crystal
99 Atmosphere
100 Brightness
101 Goblin
102 Echo Drop
103 Star Theme
104 Sitar
105 Banjo
106 Shamisen
107 Koto
108 Kalimba
109 Scotland
110 Fiddle
111 Shanai
112 Metal Bell
113 Agogo
114 Steel Drums
115 Wood Blok
116 Taiko Drum
117 Melodic Tom
118 Synth Tom
119 Reverse Cymbal
120 Fret Noise
121 Noise Chiff
122 Seashore
123 Birds
124 Telephone
125 Helicopter
126 Stadium!!
127 Gunshot
If omitted, the default instrument value 0 is used.
channel
This parameter defines which Midi channel will be associated with the player. There are 16 possible channels. Channel 10 is reserved for percussion instruments. If omitted, the default channel value 1 is used.
iterations
This parameter defines the number of iterations in the generation. Its meaning depends on the kind of grammar chosen, as explained below. If the iterations parameter has been included in the composition declarations, the latter declaration will be ignored.
Section declaring the player's local variables
The variables control the parameters of a note's attributes, as explained below.
Notes in GRAMophone
HOW NOTES ARE WRITTEN DOWN IN GRAMophone
Notes are the first category of terminal symbols GRAMophone.
GRAMophone uses the English notation for notes:
A B C D E F G
The names of notes must be written in capital letters. The flat and sharp symbols are represented by 'b' and '#' respectively; no space should appear between these symbols and the name of the note: A#, Gb, etc.
NOTE ATTRIBUTES
Notes can have four attributes in GRAMophone: octave, velocity, duration and release. The octave attribute varies between -2 and 8, while the velocity and release attributes vary from 0 to 127. If the note is written without attributes, then the following default values are used: 3 for octave, 64 for velocity and release. The current default value for duration is a crotchet. In the example, "Give me A" is written simply as A[,,,]. This means that an A is generated at the third octave, with a duration of 1/4 and a velocity and release of 64.
DEFINING THE ATTRIBUTES OF A NOTE
The attributes of a note are defined by writing them inside the square brackets which follow the name of the note, without spaces. A note can have four attributes at most and each attribute type may have only one value.
The attributes must be defined in the following order:
octave
velocity
duration
release
If all three attributes are not defined, the default value is used for the missing ones.
Here are some examples of notes with attributes:
C[2, 50+60/2, 240*4,] - plays a C at the second octave, with a velocity of 80, duration of 960 (minim with a resolution of 480) and a release of 64 (default value);
Db[4,,,] - plays a D flat at the fourth octave, using the default values for velocity, duration and release;
F#[,,,] - use the default values for all the attributes;
Incorrect examples are:
Db[3, 127, 960, 64, x] - too many attributes (x is a variable).
PAUSE
Pauses are another category of terminal symbol in GRAMophone. They are indicated by the letter R and only take a duration type attribute. If unspecified, the default resolution value is used. Attributes are defined in the same way as for notes.
Here are some examples of pauses:
R[480/2] - pause with a duration of 240;
R[] - use the default value for the attribute of type duration.
CHORDS
Chords are the final category of terminal symbol used in GRAMophone. A chord is a series of notes played simultaneously. In GRAMophone, notes played in a chord are enclosed between two '^' symbols.
Here are some examples of chords:
^C[,,,]E[,,,]G[,,,]^ - plays a C major chord, using each note's default values.
^A[2,80,240,]C[2,,240,]E[2,,240,]^ - plays an A minor chord with duration 1/8, with all notes at the second octave and velocity 64 (default value), with the first note of the chord played with a velocity of 80 and the remaining two at a velocity of 64 (default value).
THE ROLE OF R IN COMPLEX CHORDS
The notes of a chord do not always have the same duration. For example it is possible that, while the note C[2,,1920,] of duration 4/4 is playing, the musician has to play four crotchets in the following order: C[,,,], E[,,,], G[,,,], Bb[,,,]. There has to be a way of telling GRAMophone that the notes C[2,,1920,] and C[,,,] must start at the same time, that E[,,,] must begin after a pause of 1/4, G[,,,] after 2/4 and Bb[,,,] after 3/4. In GRAMophone this is written as follows:
^C[2,,1920,]C[,,,]R[]E[,,,]R[960]G[,,,]R[1440]Bb[,,,]^
In other words, every note in the chord can be preceded by a pause definition representing the time to wait before playing the note. It does not matter which order you write the notes down in a chord. The chord in the example above can also be written:
^R[]E[,,,]C[2,,1920,]R[1440]Bb[,,,]C[,,,]R[960]G[,,,]^
IDENTIFIERS
Some of GRAMophone's language entities, variables, macros and non-terminal symbols in Chomsky grammar for example, must have names by which they can be identified. These names are called identifiers and are chosen by the composer. GRAMophone's identifiers follow the system of identifiers used in the programming language Pascal. In fact an identifier is made up of a letter followed by a sequence of letters or digits. GRAMophone's identifiers must also be written in lower case.
Chomsky Grammar
NON-TERMINAL SYMBOLS
In Chomsky grammar non-terminal symbols are used to give a structure or 'style' to the musical composition. They are written with an '@' immediately followed by an identifier. The Chomsky grammar used by GRAMophone is context free so the head of the production can only be a non-terminal.
THE NON-TERMINAL SYMBOL @composition
This non-terminal symbol, which corresponds to the final composition of a single player, is obligatory.
PRODUCTION OPERATOR
This is defined by the character sequence '->' and separates the head of the production from the body.
BODY OF THE PRODUCTION
This may contain sequences of terminal (notes, pauses and chords) and non-terminal symbols. Each production must end with a semi-colon.
| (OR) OPERATOR
A production may be non-deterministic: in other words it may present two or more choices during generation. The body of a non-deterministic production is made up of the various choices separated by the | operator. For example
@non_det->A[,,,]B[,,,]@Seq1|^A[,,,]B[,,,]C[,,,]^@Seq2R[]C[,,,];
is a non-deterministic production.
MEANING OF ITERATION IN CHOMSKY GRAMMAR
In Chomsky grammar a production may include cycles, i.e. production bodies containing non-terminal symbols that refer to the production actually being produced. For example:
@Sequenza1->B[,,,]A[,,,]C[,,,]@Sequenza1;
To avoid an infinite loop during generation, the non-terminal symbol @Sequenza1 is processed an equal number of times to the iterations parameter.
Lindenmayer Grammar
Lindenmayer grammar only deals with terminal symbols and GRAMophone's version can be context-free or work in a polyphonic context. Therefore, single notes or chords can appear at the head of the production. All productions are separated by a semi-colon.
AXIOM
This is the initial production from which generation begins. It is obligatory. PRODUCTION OPERATOR
This is defined by the character sequence '->' and separates the head of the production from the body.
| (OR) OPERATOR
A production may be non-deterministic: in other words it may present two or more choices during generation. The body of a non-deterministic production is made up of the various choices separated by the | operator. For example
A[,,,]->A[,,,]B[,,,]|C[,,,]D[,,,];
is a non-deterministic production.
MEANING OF ITERATIONS IN LINDENMAYER GRAMMAR
At each step all the grammar's productions are simultaneously applied to the note string. In this case the iterations parameter represents the number of steps to be carried out.
Use of variables
DECLARATION AND INITIALISATION OF VARIABLES
GRAMophone is able to control the attributes of a note parametrically through the use of variables. These variables are declared in the player's declaration section and may be of the following types: octave, velocity, duration and msb. A variable is declared by writing its type followed by one or more identifiers separated by a comma. The declaration must end with a semi-colon. A player's identifier must be declared only once.
The following are correct declarations:
velocity x, y;
octave oct, z;
duration w;
The following are incorrect declarations:
velocity x, x;
octave z;
duration z;
Following the declaration section and before the grammar it is possible to initialise variables by means of the = operator.
The following is an example of declaration and initialisation:
velocity x;
x=0;
USING VARIABLES WITH NOTES
Variables are used in note attribute expressions. GRAMophone controls the types within expressions, so it is not possible to add an octave variable to a velocity variable, for example.
The following is an example of a note variable:
velocity x;
duration z, w;
A[4,x,z+w,].
EXAMPLE
composition "Crescendo" of "Schroeder" {
//this composition generates 64 A notes with a growing velocity
grammar chomsky
tempo 120
time_signature 4/4
iterations 64
%
player Schroeder {
instrument 40
%
velocity x=0;
@composition->A[,x=x+1,,]@composition;
}
}
CONDITIONS
In both Chomsky and Lindenmayer grammars it is possible to define conditions for the variables in the production body. If the condition is true, the production is executed; otherwise it is not. A condition is defined immediately after the name of the production by means of the '?' symbol, followed by one or more Boolean expressions.
The Boolean operators are:
! not
&& and
|| or
The relational operators are:
== uguale
!= diverso
< minore
> maggiore
<= minore o uguale
>= maggiore o uguale
The following is an example of a conditional production.
@battuta?x!=0->A[,x=x-10,,]@battuta;
which means: while x is not equal to zero, generate the @battuta production; otherwise do not.
Discography, GRAMophone's library
GRAMophone is able to include external libraries, called discographies. To include a discography in a source file, use the keyword discography followed by its file name. A discography can be included at any point in the source file, as long as its contents match the position of the source where it has been included.
Macros
Macros can be defined using the keyword define, followed by a lower-case identifier and a string placed in inverted commas. Macros must be defined at the beginning of the source composition, before the composition keyword. For example, in order to simply write a instead of A[,,,], the following macro must be defined: define a "A[,,,]"
Functions in GRAMophone
THE repeat() FUNCTION
The repeat() function takes an msb type value plus a Chomsky or Lindenmayer sequence. It enables the included sequence to be repeated a number of times that is equal to the msb type value.
THE rand() FUNCTION
The rand() function takes an expression and returns a random value which is less than the value of the expression.
Melodic operators in GRAMophone
transpose()
The transpose() operator takes an msb type value plus a Chomsky or Lindenmayer sequence. It generates a sequence in which all the notes in the relevant sequence are transposed by a number of semitones equal to the msb type value.
inversion()
The inversion() operator takes a Chomsky or Lindenmayer sequence. It generates a sequence in which the intervals between the first and the other notes in the sequence taken are calculated in reverse.
retrograde()
The retrograde() operator takes a Chomsky or Lindenmayer sequence. It generates a sequence which is the contrary of the sequence inserted.
Giovanni Ferranti <giovanni_at_giovanniferranti_dot_it>