Chord Transposer - Chord Progression Key Transposer

A chord transposer shifts an entire chord progression from one key to another while keeping the relative intervals between the chords intact. Pick the original key, the target key, the enharmonic spelling, and paste the progression; the tool returns the same progression written in the new key with chord qualities and any slash-bass notes preserved.

• • Singers moving a song to fit a vocal range: Shift a song up or down a few semitones so the melody sits in a singer's range.
• • Guitarists choosing a capo-friendly key: Move a barre-chord progression into an open key so open chords replace the barre shape.
• • Pianists accompanying a transposing instrument: Adapt a concert-key chart for a Bb clarinet, Eb alto sax, or F horn.
• • Teachers building worksheets and ear training: Generate the same progression in several keys so students can practice interval recognition.

The tool reads chord symbols as text, so triads, sevenths, slash chords, and altered extensions all move with the root. The result panel reports the underlying semitone interval so the user can sanity-check the shift.

Each semitone on the chromatic scale also has a fixed frequency ratio: one semitone up multiplies the pitch by 2^(1/12), and seven semitones up (the circle-of-fifths step) multiplies by about 1.498. A frequency calculator works through that same pitch-to-ratio relationship on any wavelength or period input.

The chord transposer assigns every pitch class a number from 0 to 11 on the chromatic scale, computes the semitone distance between the original and target key, and adds that distance to each root in the progression. The chord quality attached to each root, and any slash-bass note, moves with it.

• originalKey: The starting key of the progression, mapped to a chromatic index between 0 and 11 (C is 0, B is 11).
• targetKey: The destination key. The interval is the modular difference of the two chromatic indices.
• chordProgression: Chord symbols separated by spaces, commas, or newlines. Each symbol is split into root, optional quality, and optional slash bass.
• enharmonic: Sharp or flat spelling for the new roots. The same preference is used for slash-bass notes.

For each chord token, the parser reads the root letter plus an optional accidental and keeps the remainder as the chord quality. Minor, seventh, major seventh, minor seventh flat five, diminished, augmented, sus2/sus4, sixth, ninth, add ninth, eleventh, thirteenth, and the 5 power chord all pass through unchanged.

If the symbol contains a slash-bass note, the bass is parsed, transposed by the same interval, and re-spelled independently, so G/B becomes C/E when moved up five semitones.

According to Britannica (tuning and temperament), equal temperament divides the octave into twelve identical semitone steps, which assigns each of the twelve pitch classes a fixed position from 0 to 11 on the chromatic scale.

The wrap-around in the interval formula is modular arithmetic: interval = (targetIndex - originalIndex + 12) mod 12 always returns 0-11, and adding 12 before the mod handles the case where the target sits behind the original on the chromatic circle. A modulo calculator applies the same remainder-after-division pattern to any integer input, which lets a user confirm the wrap step-by-step on a specific key change.

Four ideas explain every transposition the chord transposer performs.

These four ideas cover every transposition the chord transposer performs: keys become integers, the interval becomes a modular difference, every root moves by that interval, and the chord quality and slash-bass note pass through. Each semitone also represents a 2^(1/12) frequency multiplier, so the count of semitones between two pitches equals log base 2 of their frequency ratio. A log 2 calculator applies that same binary-logarithm step to any positive input, which is handy when a chart lists pitches in Hz and the transposition needs to be verified by frequency rather than by name.

Five steps cover a single-chord lookup and a full progression paste with this tool.

1. 1 Pick the original key: Open the Original Key menu and choose the key the progression is in. The list covers sharp and flat spellings for the same pitch class.
2. 2 Pick the target key: Choose the key the progression should move to. The tool computes the semitone interval and shows it in the result panel.
3. 3 Choose the enharmonic spelling: Use sharp for keys with sharps in the key signature, and flat for keys with flats. The same spelling is used for slash-bass notes.
4. 4 Type or paste the chord progression: Put chord symbols in the Chord Progression field, separated by spaces, commas, or newlines. Slash chords such as G/B and extensions like F#m7b5 are recognized.
5. 5 Read the transposed progression: The result panel shows the new progression, the semitone interval, the number of chords that were transposed, and the number of unparsed tokens.

If the original key is C, the target key is G, and the progression is C Am F G7, the result is G Em C D7, a 7-semitone interval, and four chords transposed with no unparsed tokens. Setting the target to Eb instead gives Eb Cm Ab Bb7 over an 8-semitone shift, the typical retune for a Bb instrument.

A separate chord transposer calculator with the same input set, parse rules, and spelling choice is also available, so a user who lands on the alternate page first can find this version through the related-calculators list. Both tools accept the same progression text and return the same transposed progression when the inputs match, so picking one over the other is a matter of which naming convention the reader is searching for.

A purpose-built tool keeps the spelling rules, slash-bass arithmetic, and warning surface in one place.

• • Preserves chord qualities and slash-bass notes: Quality suffixes (m, 7, maj7, dim, sus4, add9) and bass notes such as G/B move with the root instead of being lost in a manual retype.
• • Shows the underlying semitone interval: The result panel lists the semitones between the original and target keys, so the user can confirm the shift before practicing the new fingering.
• • Reports unparsed tokens instead of guessing: A token that does not start with a recognized pitch letter is skipped and counted, so the user can spot typos like 'xyz' or 'H7' and fix them.
• • Sharps and flats are first-class options: The enharmonic preference is an input, so a progression in Ab major comes out as Db major when flats are picked.
• • Works on multi-line progressions in one pass: A verse, chorus, and bridge pasted as a block read together, with spaces, commas, and newlines treated as separators.

Putting the spelling rules, slash-bass arithmetic, and unparsed-token warning in one place produces a chart that is closer to a finished lead sheet than a raw key change.

The chord transposer behaves like other text-rewrite utilities that change one part of an input while leaving the rest intact. A sentence case converter applies the same idea to capitalization, fixing the first letter of each sentence without touching the words or their order, and a songwriter who keeps a folder of transposed charts will recognize the same workflow in both tools.

Three variables determine the result, and two limitations tell you when to reach for a different tool.

• • Non-chord tokens such as 'xyz' or 'H7' (letters outside A-G) are skipped and counted in unparsed tokens, so the user must check the input for typos. The tool does not guess at a root.
• • Anything after the root and its accidental is preserved verbatim and reattached to the new root, so 'C7(b9,#11)' becomes 'D7(b9,#11)' with parentheses intact. A notation library fits scores that need chord grammar validation.

These factors apply to every transposition, and the limitations tell the user when to reach for a notation library.

According to Britannica (transposition in music), transposition preserves the interval relationships inside a chord progression, so quality suffixes such as m, 7, maj7, and dim stay attached to the new root when the root moves.

According to Britannica (chromaticism), a chromatic scale is the set of twelve pitch classes used as the working alphabet for transposition, and the same constant-interval operation that defines a chromatic transposition is what this calculator applies to every root in the input.