Audio: transposition (0:18)
transposition repeats a melody three times in different keys. The transposition figure shows the score:
Transposition is the process of moving the pitch of a group of notes up or down.
Modulation and transposition are very similar and the two terms confuse everyone.
There are two types of transposition, scalar and strict:
Scalar transposition always changes the scale, hence its name. Strict transposition never changes the scale.
Scalar transposition is evident in bars 5-8 of transposition. Here, transposition has taken place from one scale to another, from major to dorian. This changes the intervals between some notes. For example, the interval between the first two notes of the original melody, C and E, is a major third. After transposition, these two notes become D and F and the interval between them is a minor third. Scalar transposition always changes the scale, which is why the intervals change.
Strict transposition is evident in bars 9-12 of transposition. All the notes have moved up four semitones and the entire piece has been transposed from the old key of C major to the new key of E major. The intervals between the notes are exactly the same in the new key as they were in the old key. Whether we call this strict transposition or modulation does not really matter, either term can be used. Strict transposition can only take place between similar scales, from a major scale to another major scale, for instance, or from a minor scale to another minor scale, or from one mode to an identical mode. Strict transposition cannot take place between two different scales.
Transposition is also classed as chromatic or diatonic. Chromatic transposition means the same as strict transposition: movement up or down by the same interval or by the same number of semitones. Diatonic transposition can include scalar transposition but it can also mean transposing notes within the same key. This is not immediately evident in transposition but bars 5-9 can be viewed as either scalar transposition from C major to D dorian or diatonic transposition within the key of C major. In essence, diatonic transposition is another way of creating a variant melody.
Transposition can take place while a piece is being written to create contrasting sections of music. Or it can be done after the piece has been written to make its performance easier for a singer to sing or a musician to play.