Musical Events¶
All individual events inherit from MEvent. Such an event can be a
a Note, a Chord, a media
Clip or anything derived from those clases.
- Media Events
Clip: an Event representing a soundfile
Within a a Chain / Voice events
can be combined (with ties or glissandi) to produce lines of any complexity.
When an event is added to a container that container becomes its
parent.
Absolute / Relative Offset¶
The offset attribute of an event determines its
start time relative to the parent container. This offset can be None,
in which case it is resolved based on the context of the event
(is the object part of a Chain / Voice, which events precede it, etc).
The resolved offset can be queried via resolveOffset(),
the absolute offset via absoluteOffset()
Example
In the following example the 2nd note (4D), which has an unset offset (offset is None),
has a resolved offset of 0.5 since it is placed after the first note (4C), which
has a duration of 0.5. Since the chain itself has an offset of 1, the resulting
absolute offset of the 2nd note is 1 + 0.5 = 2.5
>>> from maelzel.core import *
# We create a chain with two notes. The chain itself has an offset
>>> chain = Chain(["4C:0.5", "4D:1"], offset=1)
>>> chain.dump(forcetext=True)
Chain -- beat: 1, offset: 1, dur: 1.5
beat offset dur item
1 0 0.5 4C:0.5♩
1.5 0.5 1 4D:1♩
>>> chain[1].offset is None
True
>>> chain[1].resolvedOffset()
0.5
>>> chain[1].absoluteOffset()
1.5
Real-Time / Quarternote-Time¶
All time attributes (offset, dur, end) are expressed in quarternote beats.
To map a beat (measured in quarternotes) to its corresponding real-time (measured in
seconds) a score structure (ScoreStruct) is needed. Such a
score structure defines the overall structure of a score (measures, time-signatures, etc)
, providing information about the tempo and tempo changes along the timeline.