Two-member rock and pop bands are relatively rare, because of the difficulty in providing all of the musical elements which are part of the rock or pop sound (vocals, chords, bass lines, and percussion or drumming). Two-member rock and pop bands typically omit one of these musical elements. In many cases, two-member bands will omit a drummer, since guitars, bass guitars, and keyboards can all be used to provide a rhythmic pulse. The four-piece band is the most common configuration in rock and pop music. Before the development of the electronic keyboard, the configuration was typically two guitarists (one lead guitarist and one rhythm guitarist, with the latter on vocals), a bassist (typically the electric bass guitar) and a drummer (e.g. The Beatles, KISS, Jackyl, Foo Fighters, Metallica, The Clash, Creedence Clearwater Revival, The Kinks, The Fray, Sonic Youth, The Smashing Pumpkins, Arctic Monkeys, Franz Ferdinand). This is popular with bands for its versatility.