7.10.10. STRUDEL-10 — Scales & Music Theory

Writing melodies in absolute pitches (c4, e4, g4) gets old fast — every key change means rewriting every note. Strudel scales let you write in degrees (0, 1, 2, …) against a named scale. Change the scale and the same degree pattern produces a new key, mode, or mood.

7.10.10.1. Part A: `scale_pattern` — degrees against a scale

scale_pattern(notation, scale_def, sound) is a shorthand for n(notation) |> scale(scale_def) |> sound(sound). The same "0 2 4 6" against C major and C minor is a one-line A/B test:

let pat <- stack([
    scale_pattern("0 2 4 6", "C4:major") |> decay(0.2) |> gain(0.5),
    scale_pattern("0 2 4 6", "C4:minor", "sawtooth") |> sustain(0.3) |> release(0.2) |> gain(0.3) |> lpf(2000.0)
])

Major sounds bright; minor sounds dark — same degrees, different intervals.

7.10.10.2. Part B: pentatonic — only “safe” notes

"C4:major:pentatonic" maps degrees 0..4 onto C, D, E, G, A — a five-note scale with no semitone clashes, so any degree pattern always sounds consonant. Useful when you want guaranteed-pretty arpeggios without thinking about voice leading:

let pat <- scale_pattern("0 1 2 3 4", "C4:major:pentatonic") |> decay(0.1) |> release(0.2)

7.10.10.3. Part C: modes — same root, different intervals

Modes are seven-note scales that share the white-keys interval pattern but start on a different scale degree. Two of the most distinctive:

dorian — minor with a raised sixth. Jazzy, folksy.
mixolydian — major with a flattened seventh. Bluesy.

let dorian_pat <- scale_pattern("0 1 2 3 4 5 6 7", "D4:dorian") |> decay(0.15) |> release(0.2)
let mixo_pat   <- scale_pattern("0 1 2 3 4 5 6 7", "G4:mixolydian") |> decay(0.15) |> release(0.2)

The other supported modes are phrygian, lydian and locrian; all share the seven-note interval shape but rotate the starting degree.

7.10.10.4. Part D: transposition

Two ways to transpose:

Change the scale root. "C4:major" → "E4:major" — degrees stay the same; pitches shift.
Add ``transpose(semitones)``. Applied after pitch resolution, shifts every note by the given number of semitones.

let pat <- stack([
    scale_pattern("0 2 4 2", "C4:major") |> decay(0.15) |> gain(0.5),
    scale_pattern("0 2 4 2", "C4:major") |> transpose(7.0) |> decay(0.15) |> gain(0.5)
])

Above, the second voice plays the same melody a perfect fifth higher.

7.10.10.5. Part E: two octaves, same scale

Stack two scale_pattern voices at different octaves to build a bass + lead pair from one scale — switch the scale root (C4 vs C5) to move between octaves while keeping the degree pattern:

let pat <- stack([
    scale_pattern("0 2 4 3", "C4:major:pentatonic", "sawtooth") |> sustain(0.3) |> release(0.1) |> lpf(500.0) |> gain(0.4),
    scale_pattern("4 2 3 0", "C5:major:pentatonic") |> decay(0.05) |> release(0.2) |> delay(0.3) |> delayfeedback(0.3) |> gain(0.5)
])

Same scale, two octaves, two different envelopes — instant counterpoint.