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, as what one music critic called a "genre of rhythm'n'blues played by white European musicians". UK Bands such as The Animals, Cream and The Rolling Stones experimented with music from the older American bluesmen like Howlin' Wolf, Jimmy Reed and Muddy Waters. While the early blues-rock bands "attempted to play long, involved improvisations which were commonplace on jazz records", by the 1970s, blues rock got heavier and more riff-based. By the "early '70s, the lines between blues-rock and hard rock were barely visible", as bands began recording rock-style albums. In the 1980s and 1990s, blues-rock bands returned to their bluesy roots, and some of these bands, such as the "Fabulous Thunderbirds and Stevie Ray Vaughan flirted with rock stardom."
Blues-rock can be characterized by bluesy improvisation, the 12-bar blues, extended boogie jams typically focused on the electric guitar player, and often a heavier, riff-oriented sound and feel to the songs than might be found in traditional Chicago-style blues. Blues rock bands "borrow[ed] the idea of an instrumental combo and loud amplification from rock & roll". It is also often played at a fast tempo, again distinguishing it from the blues.
The core of the blues rock sound is created by the electric guitar, bass guitar and drum kit. The electric guitar is usually amplified through a tube guitar amplifier or using an overdrive effect. Often two guitars are played in blues rock bands, one playing the accompaniment riffs and chords on rhythm guitar and one playing the melodic lines and solos of the lead guitar part. While 1950s-era blues bands would sometimes still use the upright bass, the blues rock bands of the 1960s used the electric bass, which was easier to amplify to loud volumes. Keyboard instruments such as the piano and Hammond organ are also occasionally used. As with the electric guitar, the sound of the Hammond organ is typically amplified with a tube amplifier, which gives a growling, "overdriven" sound quality to the instrument. Vocals also typically play a key role, although the vocals may be equal in importance or even subordinate to the lead guitar playing; as well, a number of blues-rock pieces are instrumental-only.