17.5. Musical scales and note-name helpers

Module strudel_scales

17.5.1. Scale and note selection

degree_to_note(degree: int; root_midi: int; intervals: array<int>): float

Convert a scale degree to a MIDI note number. Degree 0 = root, 1 = second, etc.; wraps at octave boundaries so degree 7 in a major scale = root + 12. Negative degrees wrap backwards: degree -1 in a 7-note scale is the 7th one octave down.

Arguments:

  • degree : int

  • root_midi : int

  • intervals : array<int>

get_scale_intervals_by_name(scale_type: string): array<int>

Return the semitone-interval table for a named scale (“major”, “minor”, “dorian”, “pentatonic”, “blues”, “chromatic”, …). Used by tests.

Arguments:

  • scale_type : string

parse_root(root_str: string): int

Parse a root-note string (“C”, “Eb4”, “Fs3”, …) into a MIDI note number. Default octave is 3. Exposed for tests.

Arguments:

  • root_str : string

scale(pat: Pattern; scale_def: string): Pattern

Alias for set_scale. Example: n(“0 2 4”) |> scale(“C4:major”).

Arguments:
scale_pattern(notation: string; scale_def: string; sound: string = "sine"): Pattern

Shorthand for n(notation) |> set_scale(scale_def) |> set_sound(sound). Example: scale_pattern(“0 2 4 7”, “C4:pentatonic”) plays a pentatonic arpeggio.

Arguments:

  • notation : string

  • scale_def : string

  • sound : string

set_scale(pat: Pattern; scale_def: string): Pattern

Treat each event’s note field as a scale degree and map it to a MIDI note using scale_def (format “Root:Type”, e.g. “C4:major”, “D:pentatonic”). Example: n(“0 2 4 7”) |> set_scale(“C4:major”) plays C, E, G, C (one octave up).

Arguments: