Chord Builder & Reference
Build chord voicings from a root and chord symbol.
Overview
The chord builder takes a root note and a chord symbol (like Cmaj7, F#dim, Bb13#11) and returns the exact note names that make up the chord. It handles triads, seventh chords, extensions, alterations, slash chords, and most jazz shorthand, so you can move from a lead sheet to a playable voicing in seconds.
Songwriters reach for it when they encounter an unfamiliar chord symbol; arrangers use it to spell voicings cleanly across instruments; and students lean on it while learning how chord symbols map onto theory. The result is the raw set of pitches — turning them into an actual hand-position is a separate choice depending on instrument and inversion.
How it works
Every chord is a root note plus a recipe of intervals stacked above it. A major triad is root, major third (four semitones), perfect fifth (seven semitones). Minor swaps the third to three semitones. A dominant seventh adds a flat seventh (ten semitones). Extensions like 9, 11, and 13 keep stacking diatonic thirds. Alterations like b9, #11, or #5 push specific tones up or down by a semitone.
The builder parses the chord symbol, looks up its interval pattern, and offsets each interval from the root by the appropriate semitone count using 12-tone equal temperament. It also respects enharmonic spelling: a chord rooted on Bb spells its third as D, not C##, because that matches how musicians read.
Examples
Cmaj7 → C E G B
F#m7b5 → F# A C E
G7#9 → G B D F A#
Bb13 → Bb D F Ab C Eb G
FAQ
Why does the same chord sometimes get spelled differently?
Enharmonic spelling depends on the key context. A G# minor chord uses G#, B, D#; an Ab minor chord uses Ab, Cb, Eb. The pitches are the same, but the notation matches the surrounding key signature.
Do I have to play every note in an extended chord?
No. On guitar and piano, players routinely drop the fifth and sometimes the root from a 9th or 13th chord because the bass and the extensions carry the harmonic identity.
What's the difference between Cmaj7 and C7?
Cmaj7 has a major seventh (B); C7 has a flat (dominant) seventh (Bb). The maj7 sounds dreamy and stable, the dominant 7 sounds tense and wants to resolve.
How do I read a slash chord like C/E?
The chord on the left (C major) is played with the note on the right (E) as the lowest pitch. It creates a smoother bass line or an inverted voicing.
Can the tool handle suspended and added chords?
Yes. Csus2 replaces the third with a second; Csus4 replaces it with a fourth; Cadd9 keeps the third and adds a ninth on top.