The opening of "Rhapsody in Blue" is written as a clarinet trill followed by a legato, 17 notes in a diatonic scale. During a rehearsal, Whiteman's virtuoso clarinetist, Ross Gorman, rendered the upper portion of the scale as a captivating and trombone-like glissando. Gershwin heard it and insisted that it be repeated in the performance. The effect is produced using the tongue and throat muscles to change the resonance of the oral cavity, thus controlling the continuously rising pitch. Many clarinet players also gradually open the left-hand tone holes on their instrument during the passage from the last concert F to the top concert B as well. This effect has now become standard performance practice for the work.