A composer or musician may have any number of reasons to change the overall key of a musical piece. A vocalist may have difficulty singing in the original range of the song, or other musicians may find the original chords too difficult to perform on their instruments. Guitarists, for example, often find keys such as C or F to be especially difficult, while keyboards try to avoid keys such as A, E or B. It may be easier to transpose the music into a key that all instrumentalists and vocalists can agree upon.
Sometimes musical scores must be transposed in order for different instruments to play the same pitch. In order for a clarinet tuned to B flat to accompany a piano tuned to C natural, one of their scores must be transposed. Composers may also want to transpose the key of a song for dramatic effect or variety. No matter what the reason for the transposition, there are several steps which must be followed to make the change successful. Transposition is not a simple element of music theory, so beginning musicians may get a little lost at times. Here's how to transpose a musical composition.
- Begin by examining the original key of the music you wish to transpose. Is it written in a major, minor or modal key? Transposition does not require a shift in the mode of the music scale--it is all being transposed as a unit. Decide what new key you wish to use in order to change the score.
- If the song's original key is C and you need to transpose it to D in order to accommodate guitarists, then consider the D note as your new tonic. Everything else is based around D as your new starting and stopping point. If you see C in the original score, then perform D with exactly the same relationship between notes. Sometimes when you transpose music on sight, it helps to develop muscle memory of the proper notes in each key.
- Apply all of the accidentals necessary to match major or minor. If you transpose from C to D, plug in the required F sharp and C sharp notations on the new score's key signature. If you're transposing on sight, keep a mental note on the changes to F sharp and C sharp while playing.
- If you're transposing the song for dramatic effect, you may want to insert a few transitional measures or a connecting chord. Changing the key of a song in midstream can be very jarring to the audience if you don't take some time to introduce them to the changes. In the case of our transposition from C to D, a brief passage with notes like E and B mingling with the new notes F sharp and C sharp may be enough. A keyboardist or guitarist might also play a C sharp or D flat chord as a build to the D major root of the transposition.
- Transposing for different instruments in an orchestra requires some knowledge of each instrument's tuning. On a B flat clarinet, for example, the note produced with a C fingering sounds like a B flat. In order to mesh with other instruments tuned in C, the music for a clarinet must be transposed one whole step up from the original key. Many musicians learn to transpose music by sight, since only one copy of the sheet music might be available or the singer may decide to change keys at the last minute.
Transposing music is not the most difficult element of music theory, but it does require a mastery of the various key signatures and modes to be done correctly. Beginning musicians should concentrate more on musical memory as they learn how to play in different keys. Whether you are a music composer or a musician, you should develop confidence in this technique. As an exercise leading to transposition, try playing the same piece in different keys to reduce the fear of performing in difficult or uncomfortable ones.