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OpenMusic DocumentationOM 6.6 User Manual > Score Objects > Presentation
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Score Objects Presentation

Score classes enclose the musical objects that compose a score : notes , chords , chord-seqs , voices , polys . Out of convenience, we have gathered these objects in three categories : "harmonic", "rhythmic" and "polyphonic" objects.

They can be accessed via the Classes / Score menu.

Types : "Harmonic", "Rhythmic" and "Polyphonic" Objects.

  1. Harmonic objects include notes , chords and chord-seqs .

  2. Rhythmic objects include voices (internally made of measures and  groups).

  3. Polyphonic objects include polys and multi-seqs . These are "superimpositions" of objects :

    • voices on one hand,
    • chord-seqs on the other hand.

Time Representation

These objects can be classified into two temporal categories :

  • Pulsed, or rhythmic representations are based on a traditional rhythmic expression of events in time, via rhythm trees[1]. Voices and polys are pulsed representations.
  • Linear representations are based on the absolute duration of events – in milliseconds. Chord-seqs and multi-seqs are linear representations.
  • Notes and chords are atomic objects and correspond to both temporal categories.
Expressing Rhythms


Pitches in OM are usually represented in midicents.

A midicent is a cent of one MIDI unit, that is, of a half-tone.

MIDI pitch units

In MIDI, the middle C is represented by the value 60, then 61=C#, 62=D, 63=D#, etc.

In midicent, therefore, C=6000, C#=6100, ...

Midicents allow to represent microintervals, which standard MIDI values can't do : 6050 = C+1/4 tone, 6020=C+ 1/10th tone, etc.

How to Play MicroIntervals
Manipulating Pitches in OM : Basic Tools

A set of functions and conversion modules allows to manipulate midicents and pitches in general. They can be accessed via the Functions / Score /menu.

The frequency-to-midicents function converts frequencies (or lists of frequencies) to midicents.

The midicents-to-frequencies function converts midicents to frequencies.

Its input takes atoms or lists.

The name-to-midicents function converts a note name (like "C3") or a list of note names, to midicent value(s).

The midicents-to-name function converts a midicents value (or a list of values) to note name(s).

The approximate-midicents function approximates a midicents value to the closest tempered division of the octave (for isntance 4 = quarter tones).

General Score Modules

A set of score objects manipulation modules are avalable in the Functions / Score menu

  1. Rhythm Tree

    A rhythm tree expresses a rhythmic structure as a list.

    This list is made of :

    • a duration, or number of measures,

    • a list of measures.

    Each measure is made of

    • a time signature

    • a list or proportions, or rhythmic values.

    For instance : (1 (((4 4) (1 1 2))) is a rhythm of one measure, signature 4/4, with two quarter and one half note (proportions = 1/4 1/4 2/4 = 1/4 1/4 1/2).

    The term of "tree" refers to a recusrive structure: each item in the proportions list can in turn be expressed as a duration with a list of subdivisions.

    For instance the second beat in our measure could be subdivided as follows : ((4 4) (1 (1 (2 3)) 2)).

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