8.14.3. STRUDEL-03 — Mini-Notation Advanced

The four operators in this tutorial — <...>, @N, ?, and !N — are what take you from drum-machine patterns to genuinely musical phrases. They also exist purely inside the mini-notation parser: each one rewrites the parsed pattern into the same combinators (cat, weighted_fastcat, degrade, fast) you can call directly from daslang. Knowing both forms is useful: mini-notation for terseness, combinators when the input is dynamic.

8.14.3.1. Part A: Alternation with < >

Angle brackets pick one element per cycle, advancing on each cycle and looping when it runs out:

let pat <- s("<bd sd cp>")
play(pat, 6.0)

You hear bd on cycle 0, sd on cycle 1, cp on cycle 2, then back to bd. This is the cat combinator under the hood: the angle group spans one full cycle each iteration.

Inside a sequence the angle group still occupies one slot:

let pat <- s("bd <sd cp> hh hh")
play(pat, 4.0)

The <sd cp> slot alternates each cycle — snare on cycle 0, clap on cycle 1. This pattern is how you write “second beat changes” in a single line.

8.14.3.2. Part B: Elongation with @N

Postfix @N makes an element occupy N units of the parent sequence (default is 1). It is implemented via weighted_fastcat — the parser tracks weights for each token and divides the cycle proportionally:

let pat <- s("bd@3 sd") |> sustain(0.5)
play(pat, 4.0)

Without @3 each token would get half a cycle. With it the kick gets 3/4 and the snare gets 1/4. This is how you write swung or front-loaded phrases without nested brackets.

Underscore _ is the equivalent for the previous element: "bd _ _ sd" is the same as "bd@3 sd". Use whichever reads better for your phrase.

8.14.3.3. Part C: Degrade with ?

Postfix ? randomly drops events at the marked element with 50% probability. Hi-hats are the canonical use:

let pat <- s("bd hh? sd hh?")
play(pat, 6.0)

The kick and snare are reliable; the hats appear roughly half the time, varying from cycle to cycle. The drop is decided by hashing each event’s start time, so a given pattern loses the same hats on every run. It feels human, but it is reproducible — not random.

You can also write hh?0.25 to use a different drop probability — the default ? is shorthand for ?0.5.

8.14.3.4. Part D: Replicate with !N

Postfix !N repeats an element N times. The parser reads it as a modifier on the element it follows, exactly like *N, so the repeats land inside that element’s own slot:

let pat <- s("bd!3 sd")
play(pat, 4.0)

"bd!3 sd" is two slots: three kicks packed into the first half, one snare in the second. It produces the same haps as "bd*3 sd" — query both by hand and the timestamps match.

To give each repeat a slot of its own — four equal slots, three kicks then a snare — write the element out:

let pat <- s("bd bd bd sd")
play(pat, 4.0)

8.14.3.5. Part E: Euclidean rhythms with (k,n) and (k,n,rot)

Postfix (k,n) spreads k onsets as evenly as possible over n steps. bd(3,8) is the classic tresillo — three kicks across eight slots:

var pat <- s("bd(3,8)")
var haps <- invoke(pat, TimeSpan(start = 0.0lf, stop = 1.0lf))
for (h in haps) {
    print("  onset at {h.whole.start}\n")
}
play(pat, 4.0)

Querying one cycle [0,1) by hand and printing h.whole.start shows exactly where the hits land — 0, 0.375, 0.75 for the 3-in-8 tresillo. The parser rewrites (k,n) to the euclid(pat, k, n) combinator.

The three-argument form (k,n,rot) rotates the onset pattern left by rot steps — the rhythm is the same, only its starting offset moves:

var pat <- s("bd(3,8,2)")
play(pat, 4.0)

This rewrites to euclidRot(pat, k, n, rot). The function forms euclid and euclidRot are public and covered in tutorial 05 — use them directly when k/n come from variables rather than a literal string.

8.14.3.6. Where next

You now know the full mini-notation surface. Tutorial 04 leaves the parser behind and shows the time algebra — fast, slow, rev, hurry — which transforms any Pattern (mini-notation or not) by rewriting query spans.

See also

Full source: tutorials/daStrudel/daStrudel_03_mini_notation_advanced.das

Previous tutorial: STRUDEL-02 — Mini-Notation Fundamentals

Next tutorial: STRUDEL-04 — Time Manipulation

Related: Random Numbers — how degrade’s randomness is seeded