Cello , large, low-pitched musical instrument of the violin family, held between the performer's knees. It has four strings tuned C G d a (C = two C's below middle C; a = the A below middle C). Its range extends over more than four octaves. The earliest surviving cellos are two from the 1560s by the Italian violinmaker Andrea Amati. Until the late 18th century the cello was primarily a supporting instrument, playing bass lines and adding fullness to musical textures. During the baroque era unaccompanied cello suites were composed (1720?) by the German composer Johann Sebastian Bach, as were cello concertos by Antonio Vivaldi and Luigi Boccherini, the Italian composers. In the 19th century, works for the cello included concertos by Johannes Brahms and the Czech composer Antonín Dvorák. In the 20th century, composers such as the Russians Sergey Prokofiev and Dmitry Shostakovich further explored its solo capabilities. The most prominent 20th-century cellist was the Spanish-born Pablo Casals. Other leading soloists are the Russian-born Gregor Piatigorsky and Mstislav Rostropovich.
