chord generator

A scale is a sequence of notes arranged in ascending or descending order within an octave. A mode is a specific rotation or starting point of an existing scale. The major scale has 7 notes — starting that same sequence of notes on each of the 7 different scale degrees produces 7 different modes, each with a unique pattern of whole steps and half steps, and therefore a unique sound and emotional character. Practically: C major (C D E F G A B) and D Dorian (D E F G A B C) use exactly the same 7 notes — but starting on D with D as the tonal centre produces a completely different mood (darker, cooler, minor-feeling) than starting on C. The notes are the same; the context and tonal centre change everything. Understanding modes explains why jazz musicians can improvise over a Am7 chord using "G major scale" fingerings — because A Dorian = G major starting on A.

Diatonic chords are chords built exclusively from the notes of a given scale — no accidentals, no borrowed notes. In C major, diatonic chords use only C, D, E, F, G, A, and B. If you stack thirds (every other note) starting from each scale degree, you get the 7 diatonic triads (or seventh chords, if you stack one more). These chords "belong to" the key naturally — they sound consonant and resolved within it. Non-diatonic chords (borrowed chords, secondary dominants, altered chords) use notes outside the key's scale and create tension, colour, or surprise. Understanding diatonic chords is foundational: once you know the 7 chords that "live in" a key, you can construct and analyse chord progressions, write songs, and improvise with a strong theoretical foundation.

Roman numerals indicate the scale degree a chord is built on and its quality. Uppercase = major chord; lowercase = minor chord. In any major key: I (major), ii (minor), iii (minor), IV (major), V (major), vi (minor), vii° (diminished). In C major: I = C major, ii = Dm, iii = Em, IV = F major, V = G major, vi = Am, vii° = Bdim. Roman numerals are key-independent — "I–V–vi–IV" describes the same harmonic relationship in any key (C: C–G–Am–F; G: G–D–Em–C; Bb: Bb–F–Gm–Eb). This is why Roman numeral analysis is the standard language for discussing chord progressions regardless of key — it describes harmonic function, not pitch.

Borrowed chords (also called modal interchange) are chords taken from a parallel mode — a mode with the same root note but different notes. For example, in C major, the iv chord (Fm) is borrowed from C minor (C Aeolian). It introduces an Eb — not in the C major scale — creating a darker, more emotional colour. Common borrowed chords in pop and rock include: the bVII (e.g., Bb in C major, borrowed from C Mixolydian) — very common in rock ("Sweet Child O' Mine"); the iv (minor four chord) — creates a melancholic, descending feel; the bVI and bIII — borrowed from the parallel minor, used in cinematic and emotional music. Borrowed chords expand your harmonic palette without fully leaving the key — they are a controlled introduction of "outside" colour that returns home.