After studying an original piece of music, orchestrators and arrangers experiment with it and deconstruct then reassemble the piece using various combinations of instruments and musical variation to produce desired scores. Arrangers also may add vocal parts. The difference between orchestrators and arrangers is the degree to and method by which they change the original music.
Orchestrators distribute a musical composition’s parts among a larger group of instruments, assigning specific elements (passages) of a piece to particular instruments or sections to produce the desired tonal colour (variation of sound). Often, they do not make other changes to the original composition. Then they create each instrumental musical part on score paper. Often the original composer of a piece is also the orchestrator. Alternatively, the composer provides a general orchestral concept, and the orchestrator uses music notation software to prepare all of the instrumental parts in detail.
Arrangers make stylistic changes to the rhythm, genre or tempo of the original piece of music, to accommodate the requirements of a particular medium (band, orchestra, choral group, solo artist, film score, radio jingle). They may work on new arrangements of old hits. For example, they may arrange an old gospel tune in a jazz style. Alternatively, they may arrange new compositions for different media, or in different styles.
Arrangers often use synthesizers and computers to experiment with musical sounds. During recording sessions, arrangers may act as musical directors, selecting songs, scoring charts, rehearsing musicians and conducting the performance.
Orchestrators and arrangers use music notation software to copy their musical interpretations and prepare performance scores and parts for individual musicians or orchestral sections.