7.12.13. STRUDEL-13 — Samples

Oscillators cover a lot of ground but most modern music is built from samples. daStrudel loads sample banks from disk and indexes them by name, so mini-notation patterns like s("bd sd hh cp") just work.

7.12.13.1. Part A: Sample Banks

A sample bank is a directory of folders — one folder per named sound. Every audio file inside the folder becomes an indexed variation:

drums/
  bd/            ← "bd" sound
    BT0A0A7.wav  ← variation 0 (bd:0)
    BT0AADA.wav  ← variation 1 (bd:1)
    ...
  sd/
  hh/
  cp/

strudel_load_sound loads one folder under a given name. Files are sorted alphabetically, so the :0, :1, … indices are stable:

require strudel/strudel_player

strudel_load_sound("{MEDIA}/drums/bd", "bd")
strudel_load_sound("{MEDIA}/drums/sd", "sd")
strudel_load_sound("{MEDIA}/drums/hh", "hh")
strudel_load_sound("{MEDIA}/drums/cp", "cp")

Once loaded, the sounds are visible to every pattern through the mini-notation:

let pat <- s("bd sd hh cp") |> gain(0.7)

7.12.13.2. Part B: Variations

Multiple files in one sound folder are addressable as name:index:

// Alternate two kick variations per cycle
let pat <- s("bd:0 bd:1 bd:0 bd:1") |> gain(0.7)

Omitting the index (just "bd") always picks :0. Use variations to keep machine-gun patterns from sounding mechanical — even a pair of slightly different kicks feels more human than a single repeated file.

7.12.13.3. Part C: Pitch Shifting with speed

speed(factor) scales the sample playback rate. speed(2.0) is one octave up and twice as fast; speed(0.5) is one octave down and half as fast. It is tape-style pitch shifting — shorter or longer than the original:

let normal <- s("bd bd bd bd") |> speed(1.0) |> gain(0.6)
let pitched <- s("bd bd bd bd") |> speed(2.0) |> gain(0.6)

speed only affects sample playback; oscillator voices (sine, sawtooth, …) ignore it and use note() for pitch instead.

7.12.13.4. Part D: Single-file Decoding with load_audio_file

Sometimes you just want to decode one audio file — to inspect it, to feed it into your own DSP chain, or to build a custom sample bank. load_audio_file decodes WAV / MP3 / FLAC / OGG into a Sample struct:

require strudel/strudel_samples

let sample <- load_audio_file("{MEDIA}/drums/bd/BT0A0A7.wav")
print("channels: {sample.channels}\n")
print("sample_rate: {sample.sample_rate} Hz\n")
print("frames: {length(sample.data) / sample.channels}\n")

An empty Sample (length(data) == 0) signals a decode failure — always check before using the data.

7.12.13.5. Part E: Playing a Slice with begin / end_pos

begin(x) and end_pos(x) take normalized positions in 0..1 and play only the [begin, end) window of a sample. begin(0.3) skips the first 30 % of the file; end_pos(0.8) trims the last 20 %. (The setter is end_pos because end is a reserved word.)

let pat <- s("gong") |> begin(0.3) |> end_pos(0.8) |> gain(0.6)

This skips the gong’s bright attack and exposes its softer middle decay.

7.12.13.6. Part F: Granulation — chop / striate / slice

Three ways to cut a sample into n grains:

  • chop(n) cuts each event in place into n back-to-back slices — the slices stay inside that event’s own time slot.

  • striate(n) spreads n slices across the whole cycle, so successive events reveal progressively later parts of the sample.

  • slice(n, p) cuts into n slices and plays them in the order and rhythm of index pattern p — structure comes from p, the sound from the source pattern.

let chopped  <- s("gong") |> chop(8) |> gain(0.6)
let striated <- s("bd sd hh cp") |> striate(4) |> gain(0.4)
let sliced   <- s("gong") |> slice(8, note("0 2 4 6 1 3 5 7")) |> gain(0.6)

7.12.13.7. Part G: Loading a Whole Directory with strudel_load_sample_dir

strudel_load_sample_dir(root) loads every audio file directly under root, using each filename as the sound name. It is the quick way to bring in an external pack such as tidalcycles/dirt-samples. The built-in drums need no loading at all, so reach for this only when you want sounds beyond bd / sd / hh / cp:

strudel_load_sample_dir("{MEDIA}/audio")
let pat <- s("gong") |> gain(0.6)

See also

Full source: tutorials/daStrudel/daStrudel_13_samples.das

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