Blues rock

Blues rock is a fusion genre combining elements of blues and rock. It is mostly an electric ensemble-style music with instrumentation similar to electric blues and rock. From its beginnings in the early- to mid-1960s, blues rock has gone through several stylistic shifts and along the way inspired hard rock, Southern rock, and heavy metal. Blues rock continues to be an influence, with performances and recordings by several popular artists.

Blues rock started with rock musicians in the United Kingdom and the United States performing American blues songs. They typically recreated electric Chicago-style blues songs, such as those by Muddy Waters, Jimmy Reed, Howlin' Wolf, and Albert King, at faster tempos and with a more aggressive sound common to rock. In the UK, the style was popularized by groups such as the Rolling Stones, the Yardbirds, and the Animals, who managed to place blues songs into the pop charts. In the US, Lonnie Mack, the Paul Butterfield Blues Band, and Canned Heat were among the earliest exponents and "attempted to play long, involved improvisations which were commonplace on jazz records". John Mayall & the Bluesbreakers and Peter Green's Fleetwood Mac also developed this more instrumental, but traditional-based style in the UK, while late-1960s/early 1970s groups, including Ten Years After, Savoy Brown, and Foghat became more hard rock oriented. In the US, Johnny Winter, the Allman Brothers Band, and ZZ Top represented a hard rock trend.

Although around this time, AllMusic commented, "the lines between blues rock and hard rock were barely visible", there was a return to more blues-influenced styles. In the 1980s, the Fabulous Thunderbirds and Stevie Ray Vaughan, recorded their best-known works and 1990s saw guitarists Gary Moore, Jeff Healey, and Kenny Wayne Shepherd become popular concert attractions. Groups, such as the Jon Spencer Blues Explosion and the White Stripes, brought an edgier, more diverse style into the 2000s, as do contemporary artists the Black Keys.

Characteristics
Blues rock can be characterized by bluesy improvisation, the twelve-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.

Instrumentation
The core blues rock sound is created by the electric guitar, bass guitar and drum kit. Often bands also included a harmonica, usually called "a harp."

The electric guitar is usually amplified through a tube guitar amplifier or using an overdrive effect. Two guitars are commonplace in blues rock bands; one guitarist focused on rhythm guitar - playing riffs and chords as accompaniment — and the other focused on lead guitar - playing melodic lines and solos.

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.

Structure
Blues-rock pieces often follow typical blues structures, such as twelve-bar blues, sixteen-bar blues, etc. They also use the I-IV-V progression, though there are exceptions, some pieces having a "B" section, while others remain on the I. The Allman Brothers Band's version of "Stormy Monday", which uses chord substitutions based on Bobby "Blue" Bland's 1961 rendition, adds a solo section where "the rhythm shifts effortlessly into an uptempo 6/8-time jazz feel". The key is usually major, but can also be minor, such as in "Black Magic Woman".

One notable difference is the frequent use of a straight eighth-note or rock rhythm instead of triplets usually found in blues. An example is Cream's "Crossroads". Although it was adapted from Robert Johnson's "Cross Road Blues", the bass "combines with drums to create and continually emphasize continuity in the regular metric drive". Cream also uses some of the lyrics from "Traveling Riverside Blues" to create their own interpretation of the song.

History
Rock and blues have historically always been closely linked, and electric guitar techniques such as distortion and power chords were already used by 1950s blues guitarists, particularly Memphis bluesmen such as Joe Hill Louis, Willie Johnson and Pat Hare. In 1963, American rockabilly soloist Lonnie Mack created an idiosyncratic, fast-paced electric blues guitar style which confounded his contemporaries, but which later came to be identified with blues rock. His instrumentals from that period were recognizable as blues or R&B tunes, but he relied heavily upon fast-picking techniques derived from traditional American country and bluegrass genres. The best-known of these are the 1963 hit singles "Memphis" (Billboard #5) and "Wham!" (Billboard #24). However, blues rock was not named as such, or widely recognized as a distinct movement within rock, until the late 1960s, with the advent of British bands as Free, Savoy Brown and the earliest incarnations of Fleetwood Mac. The musicians in those bands had honed their skills in a handful of British blues bands, primarily those of John Mayall and Alexis Korner. At that point, Mack's earlier recordings were rediscovered and he soon came to be regarded as a blues rock pioneer. Other American performers, such as Johnny Winter, Paul Butterfield and the group Canned Heat are now also considered blues rock pioneers.

The blues rock genre was defined when John Mayall released the album Blues Breakers with Eric Clapton in 1966, which included guitarist Eric Clapton. Blues rock was a kind of rhythm'n'blues played by British musicians. Cream created a hybrid of blues with jazz experimentation which was the most innovative to date. British band Fleetwood Mac had initially blues roots inspired by Mayall and then evolved: their guitarist Peter Green brought many innovations to their music. Their music became successful in "white America" thanks in part to the operatic overtones in the vocals that captivated the audience.

The electric guitar playing of Jimi Hendrix (a veteran of many American rhythm and blues and soul groups from the early-mid-1960s) and his power trios, The Jimi Hendrix Experience and Band of Gypsys, has had broad and lasting influence on the development of blues rock, especially for guitarists. Eric Clapton was another guitarist with a lasting influence on the genre; his work in the 1960s and 1970s with John Mayall and the Bluesbreakers, The Yardbirds, supergroups Blind Faith, Cream and Derek and the Dominos, and an extensive solo career has been seminal in bringing blues rock into the mainstream. By this time, American acts such as The Doors and Janis Joplin further introduced mainstream audiences to the genre. David Gilmour of Pink Floyd is known for incorporating a mixture of blues rock, progressive rock and psychedelic rock into his guitar work. Gilmour, who has received universal acclaim (from both critics and fans alike) for his guitar work, has described Hendrix as a huge inspiration for his style of playing.

In the late 1960s, Jeff Beck, a former member of The Yardbirds, revolutionized blues rock into a form of heavy rock, taking the UK and the US by storm with his band, The Jeff Beck Group. Jimmy Page, a third alumnus of The Yardbirds, went out to form the New Yardbirds which would soon become known as Led Zeppelin and would become a major force in the 1970s heavy metal scene. The Who during their early run was a blues rock standard group, with their posters for their performances including their catch phrase "Maximum R&B". During this period the band covered songs from Bo Diddley, Sonny Boy Williamson, and Mose Allison. The Australian band AC/DC were also influenced by blues rock. Other blues rock musicians influential on the scene in the 1970s included Dr. Feelgood, Rory Gallagher and Robin Trower.

Beginning in the early 1970s, American bands such as Aerosmith fused blues with a hard rock edge. Blues rock grew to include Southern rock bands, like the Allman Brothers Band, ZZ Top and Lynyrd Skynyrd, while the British scene, except for the advent of groups such as Status Quo and Foghat, became focused on heavy metal innovation.

Blues rock had a rebirth in the early 1990s - 2000s, with many artists such as Gary Moore, Mad Season, John Norum, Gary Clark Jr., The White Stripes, Jack White,  Rival Sons, John Mayer, Blues Traveler, The Black Crowes, The Black Keys, Jeff Healey,  Clutch, The Jon Spencer Blues Explosion Joe Bonamassa, and Guy Forsyth.