How to transpose a song
September 28, 2026 · Updated September 30, 2026
Work out the interval between the old key and the new one, then move every note and every chord by that same interval. A song in G moved to A has gone up a tone, so every chord in it goes up a tone.
The interval method
Name both keys and count the distance in semitones. G to A is two semitones, a major second.
Move every chord root by that distance, keeping each chord's quality. G major becomes A major, E minor becomes F sharp minor.
Move every melody note by the same distance.
Write the new key signature, per How to find the key of a piece.
Respell anything awkward. The new key decides whether a note is written as a sharp or a flat, and the letters have to stay in order.
Step 5 is where transpositions go wrong on paper. Moving E flat up a tone gives F, and moving it up a semitone gives F flat, because the letter has to advance past E.
The scale degree method
Numbering the chords by their position in the scale removes the arithmetic entirely. Write the progression once in numbers, and it plays in every key.
| Degree | In G | In A | In C |
|---|---|---|---|
| I | G | A | C |
| ii | A minor | B minor | D minor |
| iii | B minor | C sharp minor | E minor |
| IV | C | D | F |
| V | D | E | G |
| vi | E minor | F sharp minor | A minor |
A progression written as I, V, vi, IV is the same song in all three columns. Session players and worship bands use this on purpose, because it makes a key change a spoken instruction instead of a rewrite.
Roman numerals carry the chord quality in their case, with capitals for major and lower case for minor. The Nashville number system does the same job with plain digits.
Capo, for guitar
A capo raises everything by one semitone per fret, so the shapes stay and the sounding key moves up.
| Shapes you play | Capo | Key that sounds |
|---|---|---|
| G | 2 | A |
| G | 3 | B flat |
| C | 1 | D flat |
| E | 4 | A flat |
| D | 2 | E |
Pick the shape set that keeps the open strings you want ringing. A capo cannot transpose downward, so a song that needs to drop has to move to a different shape set, or the guitar has to be tuned down.
Transposing instruments
Some instruments are written in a key other than the one they sound. A B flat trumpet sounds a major second below what is written, so the player reading a C produces a concert B flat.
| Instrument | Written note | Sounding note |
|---|---|---|
| B flat trumpet or clarinet | C | B flat, a tone lower |
| E flat alto saxophone | C | E flat, a major sixth lower |
| F horn | C | F, a fifth lower |
To write a part for one of these, go the other way: to make a B flat trumpet sound a concert F, write a G. Getting the direction backwards is the most common error in arranging, and it lands the part a whole tone out in rehearsal.
Choosing the new key
The reason to transpose is usually a voice. Find the highest and lowest note the singer holds comfortably, compare those to the song's range, and move the song until it fits inside them.
Two secondary considerations settle a tie. Instruments have keys that sit better under the hand, so guitar prefers G, C, D, E and A, and brass prefers the flat keys. And a key written with fewer accidentals is easier to read, so B major with five sharps beats C flat major with seven, even though they sound identical.
Sources
Open Music Theory, on intervals, Roman numeral analysis and transposing instruments
How to build a major scale, for why the letter has to advance when a note is respelled
How to read a chord symbol, for keeping a chord's quality intact while its root moves