Transposing is a useful skill for people who play an instrument, especially the piano, organ, or some other keyboard instrument. If a pianist is accompanying a singer and the song is a little too high for the singer’s voice, it is very useful if he is able to transpose it down so that the music sounds in a lower key. For example, if the music is written in the key of C major, it could be transposed down a whole tone so that it sounds in B-flat major.