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.
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. (February 2018)
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.
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.