MusicReasonChords and Harmony
Which scales contain this chord?
Pick a chord built on a chosen root. This tool finds every scale in the launch vocabulary, built on that same root, whose pitch-class set contains all of the chord's own tones. With no surrounding context it calls every match merely compatible; add a function context and it ranks the conventional default choice first.
Answer
Understand
A chord's own tones rarely fill a scale by themselves, so more than one scale can contain them all. C major7 (C, E, G, B) is a subset of both C Ionian and C Lydian, since both scales include those four notes plus three others. Without knowing whether the F above C should sound natural or raised, this tool cannot say which scale a player will actually want; it can only say both remain compatible until context narrows the choice.
Worked examples
C major7 matches C Ionian and C Lydian as equally compatible scales, since C major7's tones are a subset of both. C7 sharp 11 matches C Lydian Dominant, the scale whose raised fourth degree matches the chord's own sharp-11 tension exactly. A chord with no third at all, such as a sus4, leaves major- and minor-leaning scale families equally compatible; this tool reports that case as ambiguous rather than defaulting to one quality.
Method and limitations
The tool spells the chord's tones from the same locked chord-formula vocabulary Chord Builder uses, then checks every Locked scale formula built on the same root for whether its pitch-class set is a superset of the chord's. Every containing scale is returned, ranked first by whether a supplied function context marks it the conventional default for that chord quality, then by how few extra (non-chord) tones it adds. This tool never claims a single scale is "the" correct choice without that context, and a chord lacking a third produces an explicit ambiguity state rather than a forced ranking.
This tool is distinct from Scale Finder because the chord's own tones, not an arbitrary note set, are the starting evidence: the search is scoped to scales that already contain everything the chord declares, then ranked by how few additional notes each one brings in beyond that. A scale with fewer extra tones is a tighter fit around the chord, though a tighter fit is not automatically a better musical choice; a wider scale can supply useful passing tones a tighter one would not. Context, when supplied, breaks ties toward the chord quality's own conventional default rather than toward the numerically tightest fit.