Definition
Transposing means performing or rewriting a piece at a different pitch while keeping the intervals and rhythm. Besides “written-out” transposition (recalculating the notes one by one), the Italian school teaches transposition by clef change: you read the part imagining a different clef from the one written, change the key signature, and correct the accidentals. It is the method used by conductors, accompanist pianists, and anyone who reads scores with transposing instruments.
The principle
A note written on a given line changes its name depending on the clef. Take the note written on the second line:
| Imagined clef | Name of the note on the second line | Transposition relative to the treble clef |
|---|---|---|
| Treble (G, 2nd line) | G | none |
| Soprano (C, 1st line) | E | a third below |
| Mezzo-soprano (C, 2nd line) | C | a fourth above (or a fifth below) |
| Alto (C, 3rd line) | A | a second above |
| Tenor (C, 4th line) | F | a second below |
| Baritone (F, 3rd line) | D | a fourth below (or a fifth above) |
| Bass (F, 4th line) | B | a third above |
The actual octave is adjusted separately: the clef tells you the name of the note, not the register in which to play it.
The procedure in four steps
- Determine the interval of transposition (for example: a major second down).
- Choose the clef that gives the right note name (second down → tenor clef).
- Change the key signature: work out the new key (C major a major second down → Bb major, two flats).
- Correct the accidentals: an accidental that raises a note relative to the key signature in the original also raises it in the transposition. This is why a sharp can become a natural and a natural can become a flat. Example: in C major an F# (which raises the fourth degree) transposed to Bb major becomes E natural, not E#.
Applications with transposing instruments
- Clarinet and trumpet in Bb (sound a major second below what is written): read in tenor clef, remove two sharps or add two flats to the key signature.
- Clarinet in A (sounds a minor third below): read in soprano clef, add three sharps or remove three flats.
- Horn in F (sounds a perfect fifth below): read in mezzo-soprano clef, add one flat or remove one sharp, and drop down in register.
- Trumpet in D (sounds a major second above): read in alto clef, add two sharps.
Practical rules
- Before reading, pencil in the new key signature at the start of the staff: it is the step where mistakes are most common.
- Practice each clef individually (the seven clefs) before using them to transpose.
- For accompanists: the transpositions singers ask for most are a whole step or a half step. For a half step the note names do not change: only the key signature changes (for example from C major to Db major) and the accidentals are corrected.
Common mistakes
- Changing the clef but not the key signature.
- Copying the accidentals as written instead of translating their function.
- Getting the octave wrong: the imagined bass clef on a treble part gives the right name but two octaves lower.
Examples
- Mozart, Clarinet Concerto K. 622: the part is for clarinet in A, written in C major; to know what actually sounds, read it in soprano clef with the key signature of A major (three sharps).
- The horn parts in Haydn and Mozart symphonies change keys (horn in Eb, in D, in G): a conductor reads them with a different imagined clef for each piece.
- A pianist accompanying an aria written in F major who has to play it in Eb major reads in tenor clef (for the right hand) with the three-flat key signature.
How to use it in composition
- When you write for transposing instruments, the clef method lets you check the parts quickly without recalculating them note by note.
- Mentally reading orchestral scores “in C” makes it possible to do harmonic analysis of historical scores with horns and trumpets in different keys.
Exercise
- Transpose a melody in C major up a second (alto clef, key signature of D major), correcting every accidental.
- Read a clarinet in Bb part and write down the concert pitches.
- Transpose the same melody down a half step by changing only the key signature.
Connections
Staff and clefs; Transposition and transposing instruments; Key signatures; Woodwinds: ranges and transpositions; Brass: ranges and transpositions; Reading the orchestral score.