For 10 points, name this instrument, the second-largest string instrument in the modern symphony orchestra, that is played by Yo-Yo Ma.
An incomplete concerto for this instrument was found on the back of Tchaikovsky's sixth symphony, though he had already written the Rococo Variations for it. Edward Elgar wrote a concerto for this instrument in E minor which was popularized by Jacqueline du Pré, and another concerto for it is Antonín Dvorák's in B minor. Representing the title character in Richard Strauss' tone-poem Don Quixote, Pablo Casals popularized this instrument with his discovery and recording of J.S. Bach's six suites for it. For 10 points, name this instrument, the second-largest string instrument in the modern symphony orchestra, that is played by Yo-Yo Ma.
An incomplete concerto for this instrument was found on the back of Tchaikovsky's sixth symphony, though he had already written the Rococo Variations for it.
Cello