Blues rock is a hybrid musical genre combining bluesy improvisations over the 12-bar blues and extended boogie jams with rock and roll styles. The core of the blues rock sound is created by the electric guitar, bass guitar and drum kit, with the electric guitar usually amplified through a tube guitar amplifier, giving it an overdriven character. The style began to develop in the mid-1960s in England and the United States. UK Bands such as The Who, The Yardbirds, Led Zeppelin, The Animals, Fleetwood Mac, Cream and The Rolling Stones experimented with music from the older American bluesmen, like Albert King, Howlin' Wolf, Robert Johnson, Jimmy Reed, Muddy Waters, and B.B. King.