afseq
Overview
afseq, aka NerdoRhythm, is an experimental, dynamic, imperative and functional music sequence generator for Rust and Lua.
It allows you to create music sequences either in plain Rust (static, precompiled) or in Lua (dynamic, real-time). In addition to a custom imperative event generator via the rhythm config, it also supports creating events using the Tidal Cycles mini-notation via the cycle function.
afseq is part of the afplay crates.
This part of the afplay crates deals only with raw musical event generation. It does not generate audio. See the examples folder for how to combine a simple playback engine using afplay with afseq to create a simple sequencer playback engine.
Demo applications
See examples/play.rs for an example using rust only: it defines and plays a little music thing. The content can only be changed at compile time.
See examples/play-script.rs for an example using the Lua API: it also defines and plays a little music thing, but its contents can be added/removed and changed on the fly to do music live coding.
Components
A Rhythm is composed of 3 units in afseq:
- Pattern: dynamic pulse train generator to define the rhythmical pattern.
- Gate: optional pulse train filter between pattern and emitter.
- Emitter: dynamic note or parameter value generator which gets triggered by the pattern.
By separating the rhythmic from the tonal (or parameter value) part of a musical sequence, each part of the sequence can be freely modified, composed and (re)combined.
We're basically treating music in two dimensions here: the rhythmic part as one dimension, and the tonal part as another.
However, it's also possible to use just the emitter part of afseq, writing both parts in one dimension only. This can be done by using a simple never ending 1-valued train pulse as the input pattern, which defines the time grid for the emitter.
+++ Rhythm +++
~ Timebase ~
Define basic time unit and step length of a pulse.
e.g. 1 second or a quarter note or bar...
┌------------┐
│ Pattern |
└------------┘
Define basic rhythmical pattern as pulse train.
e.g. `[0, 0.5, 0, 1, [1, 1, 1]]` where the inner [] is a subdivision that
"crams" a subset of pulses into the duration of a single pulse.
↓
┌------------┐
│ Gate |
└------------┘
Passes or suppresses pattern pulses.
e.g. Probability Gate: pass 1s directly, skip 0s, values in range (0 - 1)
are passed with the pulse value as probability.
↓
┌-------------┐
│ Emitter |
└-------------┘
Generate events in a rhythmical pattern.
e.g. constantly trigger C-4, a single note for each pulse.
- or emit a single note sequence of notes for each pulse -> an arpeggio.
- or emit a sequence of chords -> a chord progression.
- or emit a todal cycle.
TimeBase
The TimeBase represents the unit of time for the rhythm, either in musical beats or wall-clock time (seconds, ms). It defines the unit and duration of a step in the sequence.
The default time unit of rhythm is one beat.
Pattern
A Pattern is a sequence of pulses that defines the musical sequence's rhythm. It consists of a list of pulses with possible subdivisions, an optional number of repeats and an optional time offset. A pattern can generate pulses using a specific algorithm, such as a Euclidean rhythm or using a fixed, predefined pattern, or by using a dynamic generator - a function.
The default pattern of a rhythm is a never ending pulse train of 1's.
Gate
A Gate is a filter that determines whether or not an event should be emitted based on a pulse value. The gate can be used to filter out pulse events or to add randomness to the rhythm. A gate can be a predefined gate from the library or a dynamic filter - a function.
The default gate in a rhythm is a probability gate, which passes 1 and 0 events as they are, and values in between (0 - 1) with a probability.
The default gate in a rhythm is a threshold gate, which passes all pulse values > 0.
Emitter
An Emitter is an iterator that generates events for each pulse value. It can be made up of a fixed list of events, tidal cycles, or it can be a dynamic generator - a function.
The default emitter spits out middle C note values for each pulse.
Examples
Rust
The rust API uses Fluent interfaces to build rhythms.
use afseq::prelude::*; fn main() -> Result<(), Box<dyn std::error::Error>> { // events can tagged with ids to e.g. trigger different instruments let KICK = InstrumentId::from(1); let SNARE = InstrumentId::from(2); let SYNTH = InstrumentId::from(2); // define a time base for the rhythm let beat_time = BeatTimeBase { beats_per_min: 130.0, beats_per_bar: 4, samples_per_sec: 44100, }; // create a kick pattern in a beat time grid let kick_rhythm = beat_time .every_nth_beat(1.0) .with_instrument(KICK) .with_pattern( vec![ Pulse::from(1.0), // Bar 1 Pulse::from(vec![0.0, 1.0]), // divide beat into two 1/8th Pulse::from(0.0), Pulse::from(0.0), Pulse::from(1.0), // Bar 2 Pulse::from(vec![0.0, 1.0]), Pulse::from(0.0), Pulse::from(0.0), Pulse::from(1.0), // Bar 3 Pulse::from(vec![0.0, 1.0]), Pulse::from(0.0), Pulse::from(0.0), Pulse::from(1.0), // Bar 4 Pulse::from(vec![0.0, 1.0]), Pulse::from(vec![0.0, 1.0]), Pulse::from(vec![0.0, 1.0, 0.0, 0.0]), ] .to_pattern(), ) .trigger(new_note_event("C_5")); // trigger a snare every two beats with an offset of a beat let snare_rhythm = beat_time .every_nth_beat(2.0) .with_offset(BeatTimeStep::Beats(1.0)) .with_instrument(SNARE) .trigger(new_note_event("C_5")); // trigger chords every 4 bars let chord_rhythm = beat_time .every_nth_bar(4.0) .with_instrument(SYNTH) .trigger(new_polyphonic_note_sequence_event(vec![ vec![ new_note(("C 4", None, 0.3)), new_note(("D#4", None, 0.3)), new_note(("G 4", None, 0.3)), ], vec![ new_note(("C 4", None, 0.3)), new_note(("D#4", None, 0.3)), new_note(("F 4", None, 0.3)), ], vec![ new_note(("C 4", None, 0.3)), new_note(("D#4", None, 0.3)), new_note(("G 4", None, 0.3)), ], vec![ new_note(("C 4", None, 0.3)), new_note(("D#4", None, 0.3)), new_note(("A#4", None, 0.3)), ], ]), ); // combine patterns into a phrase to play them together let phrase = Phrase::new( beat_time, vec![ RhythmSlot::from(kick_rhythm), RhythmSlot::from(snare_rhythm), RhythmSlot::from(chord_rhythm), ], BeatTimeStep::Bar(8.0), ); // print first 100 events for (_rhythm_index, event) in phrase.into_iter().take(100) { println!("Event: {:?}", event); } Ok(()) }
Lua in Rust
The Lua API uses configuration tables.
use afseq::prelude::*; fn main() -> Result<(), Box<dyn std::error::Error>> { // events can tagged with ids to e.g. trigger different instruments let KICK = InstrumentId::from(1); let SNARE = InstrumentId::from(2); let SYNTH = InstrumentId::from(2); // define a time base for the rhythm let beat_time = BeatTimeBase { beats_per_min: 130.0, beats_per_bar: 4, samples_per_sec: 44100, }; // create a kick pattern in a beat time grid let kick_rhythm = new_rhythm_from_string( beat_time, Some(KICK), r#" return rhythm { unit = "1/4", pattern = { 1, { 0, 1 }, 0, 0, 1, { 0, 1 }, 0, 0, 1, { 0, 1 }, 0, 0, 1, { 0, 1 }, { 0, 1 }, { 0, 1, 0, 0 } }, emit = "c5" } "#, "kick rhythm.lua", )?; // trigger a snare every two beats with an offset of a beat let snare_rhythm = new_rhythm_from_string( beat_time, Some(SNARE), r#" return rhythm { unit = "beats", pattern = { 0, 1 }, emit = "c5" } "#, "snare rhythm.lua", )?; // trigger chords every 4 bars let chord_rhythm = new_rhythm_from_string( beat_time, Some(SYNTH), r#" return rhythm { unit = "bars", resolution = 4, emit = sequence( note("c4", "d#4", "g4"), note("c4", "d#4", "f4"), note("c4", "d#4", "g4"), note("c4", "d#4", "a#4") ):volume(0.3) } "#, "chord rhythm.lua", )?; // combine patterns into a phrase to play them together let phrase = Phrase::new( beat_time, vec![ RhythmSlot::from(kick_rhythm), RhythmSlot::from(snare_rhythm), RhythmSlot::from(chord_rhythm), ], BeatTimeStep::Bar(8.0), ); // print first 100 events for (_rhythm_index, event) in phrase.into_iter().take(100) { println!("Event: {:?}", event); } Ok(()) }
Lua
The Lua API also contains various tools to ease creating patterns.
--trigger notes in an euclidean tripplet pattern return rhythm { unit = "1/8", resolution = 3/2, pattern = pattern.euclidean(6, 16, 2), emit = { "c3", "c4 v0.5", "d3", "e4", "f4", "c2" } } --trigger notes in a seeded, random subdivision pattern math.randomseed(23498) return rhythm { unit = "1/8", pattern = { 1, { 0, 1 }, 0, 0.3, 0.2, 1, { 0.5, 0.1, 1 }, 0.5 }, emit = { "c4" }, }
... and tools to ease working with chords and scales:
-- trigger a chord sequence every 4 bars after 4 bars return rhythm { unit = "bars", resolution = 4, offset = 1, emit = sequence("c4'm", note("g3'm7"):transposed({0, 12, 0, 0})) } -- trigger chord arpeggios from a tritone scale in euclidean patterns local tritone = scale("c5", "tritone") return rhythm { unit = "1/8", emit = pattern.from(tritone:chord(1, 4)):euclidean(6) + pattern.from(tritone:chord(5, 4)):euclidean(6) }
Patterns and emitters can be Lua functions to create dynamic contents:
-- probability pattern with humanized notes return rhythm { unit = "1/8", pattern = {0, 1, {1, 0.8}, 0, 1, {1, 0.8, 0.5}}, emit = function (context) if context.pulse_time <= 0.5 then return note("c5 v0.5"):with_delay(math.random() * 0.05) else return "c5" end end } -- trigger different chords depending on the generator step count return rhythm { unit = "1/1", resolution = 2/3, emit = function (context) local step = math.floor((context.step - 1) / 10) if step % 4 == 0 then return note("c4'm", "c2", 'off') else return note("c4'm7", "c2", (step % 3 == 0) and "f4" or "g4") end end } -- notes can be generated using the Tidal Cycles mini-notation as well -- each pattern pulse then triggers a cycle iteration -- see https://tidalcycles.org/docs/reference/mini_notation/ return rhythm { unit = "1/1", emit = cycle("<c4 e4 g4> <e4 g4> <g4 [a4|c4] d5> <b4 [f#4|e5]>") }
See example scripts folder and Lua API definitions for more info and examples.
License
afseq is distributed under the terms of the GNU Affero General Public License V3
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