Coming from Strudel or TidalCycles

claudius borrows Strudel’s mini-notation and many of its pattern methods, so most of your patterns carry over. The model around them is different: a Strudel program is a live loop, and a claudius script describes a song (sections, an arrangement, a mix) that is rendered and judged. This page lists every difference that changes what you write.

The same groove in both

Strudel:

setcpm(124/4)
stack(
  s("bd*4, [~ cp]*2, [~ hh]*4").bank("RolandTR909"),
  note("<a1 f1 d2 e2>").struct("~ x ~ x ~ x ~ [x x]").s("sawtooth").lpf(800),
  n("<0 2 4 6>").scale("A:minor").s("piano").room(0.5)
)

claudius:

blank("house");
tempo(124); key("A minor");
track("drums", s("bd*4, [~ cp]*2, [~ hh]*4").bank("RolandTR909"));
track("bass",  note("<a1 f1 d2 e2>").struct("~ x ~ x ~ x ~ [x x]").s("saw_bass").lpf(800));
track("keys",  n("<0 2 4 6>").scale("A:minor").octave(4).s("piano").room(0.5));

Each pattern becomes a named track, the tempo is in BPM, and the sounds are claudius’s: saw_bass is a synth preset, piano a sampled grand, and the Strudel bank name RolandTR909 is an alias of the tr909 pack.

Time

• One cycle is one bar, always. There is no setcps or setcpm; tempo(bpm) sets the song’s tempo, and a cycle lasts four beats of it.
• Patterns play inside sections. A track plays in the sections that list it, and every section starts the pattern from cycle 0: alternations, every() and random choices start over. There is no global clock running through the song.
• Queries return whole events whose onset falls in the span, never fragments. An event longer than a bar exists only in the bar where it starts, though it still sounds for its full length, and .struct(), .mask() and the controls still find it in the bars after (see Patterns and time).

Syntax

Mini-notation

Most of it is identical. The differences (full list):

• { } is a plain group: no polymeter, no %. A fractional .fast() runs a figure across bar lines instead (see Polymeter).
• . is not a separator; it is an error.
• Weights inside < > are ignored: write <a!3 b> to hold a for three cycles.
• * and / take numbers, not patterns, above 0 and up to 256 (so do fast(), slow() and ply()).
• a ! 3 is three as.
• | and , at the same level group differently; bracket the choice: [a | b], c.

Euclidean rhythms are Strudel’s: bd(3,8), bd(5,8,2) and .euclid(7, 16) give the same steps in both. So do slash chords and applied chords, which stay one word: chord("<Am F/A C G>"), chord("<I V7/V>").

Values and controls

• n() is always scale degrees. In Strudel, n() without .scale() is a sample index (or a note number). In claudius, n("0 2 4") without a scale uses the song’s key, and the sample index is bd:3 or the method .n("0 3") on an s() pattern.
• .transpose() is always semitones; .add() adds to the value. On note() both move semitones; on n(), .add(2) moves two scale degrees and .transpose(12) moves an octave. On chord(), .add() moves the voicing range and .transpose() the voiced notes (see add() and transpose()).
• .gain() is velocity. It is how hard a note is played (0 to 1), not an amplitude multiplier: claudius levels every track to its mixing role, so the track’s loudness is set with .level(dB) or mix(). .velocity() is the same control and wins when both are set.
• Note names default to octave 3, as in Strudel: note("c") is C3, MIDI 48.

Effects are per track

Strudel effects are controls on each event; claudius effects belong to the track:

A patterned effect argument is an error: .lpf("<400 2000>") raises lpf needs a number. Filter movement comes from the arrangement instead (an intro’s filter_in, a build’s highpass sweep).

Sounds

• .s() on a note pattern sets the track’s instrument; it takes one name, not a pattern, so a note pattern cannot switch instruments from event to event. Use two tracks.
• sawtooth, square, triangle and sine are not sounds; use a synth preset (saw_bass, pluck, square_lead, sub_bass …).
• Drum names are the usual bd sd cp hh oh rd cr lt mt ht rim cb sh. Without .bank() they play claudius’s synthesized drum voices; with .bank("tr909") (or RolandTR909, 808, acoustic …) the recorded machines. A bank can also go in the word, s("tr909:bd*4, tr808:cp*2"), to mix machines in one pattern; a number after the last colon is the sample index (tr808:sd:3).
• A sound pattern with several names is split into one track per name when arranged (drums.bd, drums.hh), so each is mixed by its own role.

Methods

Available, with the same meaning: fast slow late early rev ply every lastOf sometimes often rarely almostNever almostAlways sometimesBy off superimpose degrade degradeBy struct mask euclid euclidRot gain velocity legato add transpose n s sound bank scale voicing arp. Differences in detail:

• ply() and every() take integers; .every(4, f) is the first bar of every four, like Strudel’s firstOf.
• .arp() takes a mode ("up", "down", "updown"), not an index pattern.
• .voicing() takes a MIDI range; voice leading is always on.
• Randomness is seeded by the code, not by the cycle alone: two tracks with the same pattern make the same choices.

Not available: continuous signals (sine, saw, rand, perlin, range, segment), jux, sample slicing (chop, striate, slice, splice, begin, end, speed, loopAt, fit), chunk, iter, palindrome, echo/stut, when, ADSR and filter-envelope controls, vowel, and the live-coding commands (hush, setcps).

What claudius adds

• A song: sections with energies, builds, gaps, impacts and fills.
• Harmony the song knows about: prog(), Roman numerals, chord("prog"), and chord("prog").root() for a bass line that follows it.
• Parts written by music theory, drum grammars and genre profiles (song()).
• A mix: roles, target levels, sidechain, buses, a mastered result at a LUFS target.
• A critic that tells you what to fix, and evolution that tries fixes for you.