Classical music can be for instruments or for the voice. The symphony orchestra is the most common group of instruments for the playing of classical music. It has four families of instruments: the string instruments which include the violins, violas, cellos and piano, the woodwind instruments which include flutes, oboes,clarinets and bassoons together with related instruments of different sizes, the brass instruments: trumpet, trombone, tuba and French horn, and percussion instruments which nearly always includes timpani as well as many other possible instruments which are hit or shaken. This is very different from a typical rock band which has a drummer, a guitarist, one or two singers and an electric bass and keyboard. Instruments that play classical music are not normally amplified electronically.