Score Structure

This module defines a Score Structure class (ScoreStruct)

A ScoreStruct holds the structure of a score (its skeleton): it is a list of measure definitions (see addMeasure()), where each measure definition includes a time-signature, tempo and optional annotations. A ScoreStruct provides utilities to convert between score locations, quarternote time and absolute time position.

Key Concepts

Structure ≠ Contents

A ScoreStruct does not hold any actual content (notes, chords, silences, etc), it just provides a skeleton to organize such content within the given structure

Beat time vs Real time

Real time is the actual clock time, measured in seconds. Beat time refers to a symbolic time, measured in quarternotes. For example, an event (a note) starting at beat=2.5 with a duration of 0.5 beats means that the event starts 2+1/2 quarternotes after the beginning and has a duration of an eighth note. The exact location in Real time depends on the tempo and on any tempo changes before and during the event.

To convert between beat time and real time see beatToTime() and timeToBeat().

Score Location

As mentioned above, beat time is measured in quarternotes since the beginning. Within a score with time-signature changes there is a more convenient way to indicate time: a ScoreLocation, which is basically a tuple (measure index, beat offset). See locationToTime(), timeToLocation()

Note

Measure indexes start at 0

Rational Numbers

To avoid rounding errors, any variable or attribute dealing with time (in beats, seconds, tempo, etc) is represented as a rational number

ScoreStruct and maelzel.core

The ScoreStruct class is used extensively in maelzel.core. Within this context a ScoreStruct can be used as a context manager to set a temporary score structure:

from maelzel.core import *
from maelzel.music.scale import *

scale = Chain([Note(m, 0.5) for m in pitchscale('3F', steps='minor-harmonic', endpitch='5F')])
scale.show()
_images/scale-fminor-44.png 
with ScoreStruct(timesig=(5, 8), tempo=72):
    scale.show()
    scale.play()
_images/scale-fminor-58.png

Functions

measureBeatStructure(timesig, quarterTempo)

Returns the beat structure for this measure

Classes

ScoreStruct([score, timesig, tempo, ...])

A ScoreStruct holds the structure of a score but no content

MeasureDef(timesig, quarterTempo, parent[, ...])

A MeasureDef defines one Measure within a ScoreStruct (time signature, tempo, etc.)

TimeSignature(*parts[, subdivisions])

A time signature