The "Rhapsody" for clarinet was composed by Willson Osborne. Originally composed as a work for solo bassoon (accepella), it soon became the most widely performed work of its kind. It was eventually transcribed for solo clarinet as it is rendered here by the GPO solo clarinet. This work is continuously changing throughout, a new meter practically every measure. Thus providing an extremely challanging and interpretive work for the musician.
P.S. For those who are interested I also rendered it for bassoon in its original bass cleff interval;