Chord transposer: move a progression to any key

What transposing chords means

Transposing moves every chord by the same interval, so the progression keeps its shape and only its pitch changes. Moving C Am F G from C major to E major gives E C♯m A B. Each chord moved up a major third, and the relationship between the chords — I vi IV V — did not move at all. That is why a song still sounds like itself in a key that suits a different voice or instrument. Transposition covers the idea in full.

To a key, or by semitones

Choose To a key when you know where you want to end up — the singer wants it in E major. Choose By semitones when you only know how far: two semitones up turns C Am F G into D Bm G A, now in D major. Both are the same operation; the semitone count is just the distance between the two keys. The circle of fifths shows how each move changes the key signature.

Why chord types stay the same

A minor seventh chord is a minor seventh chord in every key, so a transposer must move the root and keep everything after it. Dm7 G7 Cmaj7 Cadd9 in C major becomes Gm7 C7 Fmaj7 Fadd9 in F major: the m7 stays m7, the dominant 7 stays 7, and the add9 keeps its added ninth. The tool reads each chord into Tomus’s chord list rather than shuffling letters, which is how it knows Cadd9 is C – E – G – D and not just “C with something after it”.

Why the spelling changes

A key decides how its notes are written. Up a semitone from C major is D♭ major, so C Am F G becomes D♭ B♭m G♭ A♭ — not C♯, A♯m, F♯ and G♯, which sound the same but belong to a key with seven sharps. Going the other way, up a major third to E major, the A minor chord becomes C♯m, never D♭m, because in E major the sixth degree is C♯. The transposer moves letters and accidentals together, by interval, so the result is always spelled for the key it lands in. Enharmonic notes explains why one key can have two names.

Occasionally a key would need a double flat — ♭III in G♭ major is B𝄫. The tool then writes the chord the way a player reads it (A) and shows the exact spelling beside it, so nothing changes without you seeing it. Choosing a key with fewer accidentals (F♯ major instead of G♭) avoids that altogether.

Slash chords and inversions

A slash chord names a chord and the note under it: C/E is C major with E in the bass. The bass moves with the chord, so C/E F G7/B C in C major becomes A/C♯ D E7/G♯ A in A major. Both slash chords have their chord’s third in the bass — first inversions — which the Roman numerals show with figures: I6 IV V6/5 I. Chord inversions explains the figures.

Roman numerals: what stays the same

Roman numerals name each chord by its place in the key, so they are exactly what transposition preserves. C E7 Am A7 Dm G7 C in C major reads I V7/vi vi V7/ii ii V7 I; in E♭ major it becomes E♭ G7 Cm C7 Fm B♭7 E♭, with the same numerals. The E7 and A7 are secondary dominants: they borrow the pull of a dominant to point at the next chord, and the tool marks them that way only when that chord actually follows. Minor keys work the same way — Am Dm E7 Am in A minor is Em Am B7 Em in E minor, i iv V7 i in both. Roman numerals covers the notation.

The key is detected from the chords themselves — which notes they use, and which chords open and close the progression — and the tool says when that is uncertain. Three or four chords can fit a major key and its relative minor equally well; the transposed chords are the same either way, but the numerals are not, so you can pick the key yourself.

How capo transposition works

A capo clamps the strings at a fret and raises everything you play by that many semitones. To sound in an awkward key, play shapes from an easier key lower down: the song still sounds in E♭ major while your hands play something friendlier.

The tool ranks capo positions by how many chords then have a common open-position shape in standard tuning, and prefers the lower fret when two are equal. It is a list of familiar shapes, not a model of fingering, so treat it as a starting point. The music theory for guitar guide has more on why shapes move.

What it reads, and what it does not

Chord symbols separated by spaces, bar lines or spaced dashes, on one line or several: major, minor, diminished, augmented, sus2, sus4, 6, 7, maj7, m7, m(maj7), m7♭5 (ø), dim7 and add9, each with an optional slash bass. Common ways of writing them work too — min, -, M7, Δ, °, + and so on. Ninth, eleventh and thirteenth chords, m6, 7sus4, power chords and altered dominants are not in Tomus’s chord list yet; the tool names any chord it cannot read instead of guessing, and transposes the rest. It does not read lyrics with chords above them — paste the chords only.

To work out a chord from the notes you are playing, use the chord identifier. To hear the common progressions in every key, try the chord progression explorer, and to see why a progression works, the chord progression analyzer. Every key’s chords are listed on its key page.