Struct StepScale 

pub struct StepScale { /* private fields */ }

A scale built by walking a cycle of intervals from a tonic.

use music21_rs::{Pitch, StepScale};

let tonic = Pitch::from_name("C4")?;
let cyclical = StepScale::cyclical(tonic.clone(), &["m3", "M3"])?;
let names: Vec<String> = cyclical.pitches()?.iter().map(|p| p.name()).collect();
assert_eq!(names, ["C", "E-", "G"]);

let repeating = StepScale::octave_repeating(tonic, &["m3", "M3"])?;
let names: Vec<String> = repeating.pitches()?.iter().map(|p| p.name()).collect();
assert_eq!(names, ["C", "E-", "G", "C"]);

Interval implements neither PartialEq nor Hash, so neither is derived here; compare realized pitches instead.

Implementations

impl StepScale

pub fn cyclical(tonic: Pitch, steps: &[&str]) -> Result<Self>

Builds music21’s CyclicalScale: the intervals walked once, no closing.

An empty list defaults to a single m2, as music21 does.

pub fn octave_repeating(tonic: Pitch, steps: &[&str]) -> Result<Self>

Builds music21’s OctaveRepeatingScale: the intervals plus a closing interval that completes the octave.

An empty list defaults to a single m2, as music21 does.

The closing interval is the complement of the interval sum, which is how music21 derives it — not the interval between the last realized pitch and the octave. The two differ in spelling whenever realization respells a degree: three m2 steps from C sum to dd4, whose complement is AA5, so the scale closes on B# rather than C. Taking it from the realized pitches would read the answer off already-simplified output and lose that.

music21’s own behaviour for a cycle wider than an octave is erratic — ["P5", "P5"] returns pitches an octave above the tonic it was given, and it mutates the caller’s interval list in place. Neither is reproduced here: the cycle is closed at the octave above the last pitch and the input is left alone.

pub fn sieve(tonic: Pitch, expression: &str) -> Result<Self>

Builds music21’s SieveScale from a Xenakis sieve expression.

The sieve’s interval widths become the cycle, which music21 then treats as a CyclicalScale — so "3@0" from C is C E-, and the major-scale sieve gives a major scale.

music21’s SieveScale also takes an eld (elementary displacement) to scale the widths for non-semitone steps. Only the default of one semitone is supported here, since the crate has no microtonal step type to widen to.

pub fn tonic(&self) -> &Pitch

Returns the tonic pitch.

pub fn steps(&self) -> &[Interval]

Returns the step intervals, including any closing interval.

pub fn degree_count(&self) -> usize

Returns the number of steps, which is one fewer than the pitch count.

pub fn pitches(&self) -> Result<Vec<Pitch>>

Returns the pitches of one pass through the cycle, starting at the tonic.

Trait Implementations

impl Clone for StepScale

fn clone(&self) -> StepScale

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for StepScale

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.