An arrangement is a modified version of a work. Arrangements are frequently made so that music can be performed by a different instrument or group of instruments than the original, such as an arrangement for solo piano of a symphony, concerto or other orchestral work, or an arrangement for violin of a piece originally written for the flute. Another major reason for making arrangements is to simplify difficult pieces so that they can be played by students and others with less advanced skill levels. Arrangements are also frequently made using different styles in order to make the music suitable for different audiences, such as an orchestral version of a popular song or a simplified version of a complex orchestral work.
Arrangements may be created by the original composer, by another composer, or by some other person, such as a professional arranger or a specialist player of some instrument. Some truly outstanding performers are capable of making arrangements on the fly, such as reading the score for an orchestral work and simultaneously arranging it in his or her head and playing it on the piano.