From Academic Kids
Rock band (or rock group) is a generic name to describe a group of musicians specializing in a particular form of electronically amplified music. Deriving its name from the musical style which was its immediate progenitor, rock and roll, the type of music played by rock bands has its roots deeply steeped in both rock and roll, and its immediate forebear, rhythm and blues. A rock band tends to have a heavy focus on certain instruments principally electric guitar, bass guitar, and drums (prime examples of this are Cream, The Jimi Hendrix Experience or more recently U2). Later in the 1960s, certain rock bands such as Pink Floyd and Hawkwind experimented with electric organs and synthesisers. Other instruments deployed within the context of a rock band include the electric violin, as used by Curved Air and the flute played by Ian Anderson of Jethro Tull. Another instrument common in some rock bands is the musical keyboard.
Many rock bands include two types of guitar players, a rhythm guitarist and a lead guitarist. The rhythm guitarist works closely with the bassist and the drummer as they drive both the beat and melody, while the lead guitarist is driving the second accompaning melody, as well as the solos.