A symphony orchestra is a large ensemble of musicians who variously play strings (violins, violas, cellos, basses), woodwinds (clarinets, oboes, flutes, bassoons), brass (trumpets, French horns, trombones and tubas) or percussion (drums, timpani, bells, etc.). Because of its size (100 or more musicians), an orchestra requires a conductor to keep the players together and present a unified interpretation. Compositions for the orchestra include such works as symphonies and concertos (for soloist and orchestra). Classical music is also written for, and performed by, smaller groups of instruments ("chamber music") or even by just one or two musicians ("solo recital").