<P> In traditional Western notation , the scale used for a composition is usually indicated by a key signature at the beginning to designate the pitches that make up that scale . As the music progresses , the pitches used may change and introduce a different scale . Music can be transposed from one scale to another for various purposes , often to accommodate the range of a vocalist . Such transposition raises or lowers the overall pitch range , but preserves the intervallic relationships of the original scale . For example , transposition from the key of C major to D major raises all pitches of the scale of C major equally by a whole tone . Since the interval relationships remain unchanged , transposition may be unnoticed by a listener , however other qualities may change noticeably because transposition changes the relationship of the overall pitch range compared to the range of the instruments or voices that perform the music . This often affects the music 's overall sound , as well as having technical implications for the performers . </P>
if a piece of music is perceived to have changed key then we say the piece has
transposition