a track sequences configurations for a single instrument over time. it schedules onsets, which are discrete time points at which an instrument is triggered with a given configuration.

track
  onsets: time, ...
  instrument(instrument_configuration(t))

tracks define the lowest-level temporal structure in musical arrangement.

a riff coordinates multiple tracks to form a polyphonic or layered musical phrase. tracks within a riff are typically aligned in time but may differ in density, instrument, or configuration space.

a rifftrack sequences a single riff over time. this enables reuse and repetition of musical material with or without variation. it may include temporal transforms such as transposition, time-stretching, or amplitude scaling applied per riff instance.

a song combines multiple rifftracks over time to form a complete musical structure. rifftracks may be layered, interleaved, or independently varied, allowing both vertical and horizontal musical complexity.

onsets are typically defined by the time intervals between them. these intervals may be uniform or irregular.

• fill: evenly inserts additional onsets into existing gaps
• shift: offsets the entire sequence forward or backward in time
• echo: duplicates onsets with a fixed delay, creating repetitions
• reflection: mirrors an onset sequence around a temporal pivot point

structural operations on onset sequences include:

• split: divides a sequence into segments
• merge: concatenates multiple sequences into one

onsets can be encoded using different representations, each with different implications for editing, performance, and algorithmic manipulation:

• bitstring: a binary vector where 1 represents an onset, and 0 represents a rest
• individual intervals: a list of durations between successive onsets
• cumulative intervals: a list of absolute time positions from the start

• meter: the underlying temporal grid or framework (e.g. 4/4, 6/8) that provides regular pulse divisions. all rhythmic events are positioned in relation to this grid.
• onsets: the discrete time points at which events (e.g. notes, accents) occur. these form the skeleton of a rhythm.
• duration: the length of time between onsets, or of sustained events. durations can be fixed or fluid, depending on context.
• accentuation: the dynamic weight or emphasis of an event, contributing to perceived groove or phrasing.

• expectation & coherence: rhythmic coherence arises from repeated patterns and their variation.

  • parallelism: simultaneous occurrence of similar patterns

  • serialism: rigidly ordered sequences of rhythmic values

  • polyrhythm: superimposition of two or more rhythmic cycles with distinct periodicities

  • adherence: how closely patterns follow or deviate from an established grid or motif

rhythms are categorized by how they relate to the underlying meter:

• metric: aligned with the principal beats of the meter
• intrametric: nested subdivisions within those beats
• contrametric: off-beat placements that play against expected emphasis
• extrametric: timings that span beyond or ignore bar lines, establishing higher-order or free-form structures

• additive: rhythm is formed by concatenating intervals of varying lengths (e.g. 3 + 2 + 3). this is typical in many folk and non-western traditions.
• divisive: rhythm is formed by evenly dividing a span of time (e.g. dividing a beat into 2 or 4 equal parts). this is common in western classical and pop traditions.

both methods can be layered or mixed to form rich hybrid structures.

in the context of digital synthesis and signal-based models:

• rhythms define when and how parameters change (eg amplitude pulses, pitch shifts, filter modulations)
• they are represented via discrete-time onset functions or binary sequences
• rhythms are often modular and composable, allowing them to be reused or transformed across instruments and layers