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Key Transpose Calculator

Transpose musical keys by semitones for instruments and vocals. Convert between major and minor keys with correct sharp or flat notation.

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Inputs that matter
Original Key, Semitones to Transpose
Output to expect
Key Transpose Calculator
  • Check the units and required inputs before comparing results.
  • Keep the assumptions with a copied result so you can reproduce the calculation later.
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Reference & details

How it works

Semitone Transposition

Add semitones to pitch class number (C=0, C#=1... B=11). Wrap at 12 for octave equivalence.

New pitch class = (Original + Semitones) mod 12

Key Signature Mapping

Transposing up a fifth adds one sharp (or removes one flat). Down a fifth adds one flat.

Major keys follow circle of fifths; +7 semitones = up a fifth

Enharmonic Equivalence

Choose notation with fewer accidentals. Transpose G major up 1 semitone → G# major (8 sharps) or Ab major (4 flats) — prefer Ab.

F# major ≡ Gb major (6 sharps vs 6 flats)

Updated: July 2026

Example Scenarios

Song in E major transposed down 3 semitones → C major — comfortable for alto range without losing song character.

Song in G with capo on 3rd fret plays in Bb major. Transpose chart: written G shapes sound Bb.

Trumpet in Bb reading C major sounds Bb major. Written part must be transposed up 2 semitones from concert pitch.

FAQ

12 semitones (half steps) equal one octave. Transposing up 12 semitones returns to the same key name (different octave).

Capo fret number equals semitones up. Capo 3 on G major shapes = Bb major sound. Add capo semitones to written key for sounding key.

Same semitone math applies. A minor up 3 semitones = C minor. Relative major/minor relationship preserved (Am ↔ C, Em ↔ G).

Bb instruments: written note sounds 2 semitones lower. Eb alto sax: sounds 9 semitones lower (major 6th). Add interval to find concert pitch.

Prefer key signature with fewer accidentals. After transposition, if result has 5+ sharps, consider enharmonic flat key equivalent.

About Key Transpose Calculator

Transposing music changes the key by shifting every note by the same interval. Enter the original key and number of semitones (or target key) to calculate the transposed key with correct sharp or flat notation.