Hard rock or heavy rock is a sub-genre of rock music which has its earliest roots in mid-1960s garage and psychedelic rock and is considerably harder than conventional rock music. It is typified by a heavy use of distorted electric guitars, bass guitar, drums, pianos, and other keyboards.

Characteristics

Hard rock is strongly influenced by blues music; the most frequently used scale in hard rock is the pentatonic, which is a typical blues scale. Unlike traditional rock and roll (which takes elements of the "old" blues), hard rock incorporates elements of "British blues", a style of blues played with more modern instruments such as electric guitars, drums, keyboards and electric bass. A notable departure from traditional blues forms is that hard rock is seldom restricted to the I, IV, and V chords prevalent in twelve or sixteen bar blues, but includes other chords, typically major chords rooted on tones of the minor scale.

The term "hard rock" is often applied to many styles of rock music, their only common feature being that they deviate from pop rock, though this is generally incorrect. Two such examples are punk rock and grunge. Punk rock uses a faster tempo, less melody, fewer riffs (often using barre chords), more aggression and anti-establishment lyrics.

Beginnings (1960s)

As stated, one of the major influences of hard rock is blues music, especially British blues. British rock bands, such as Cream, The Rolling Stones, The Yardbirds, The Who and The Kinks modified rock and roll, adding to the standard genre harder sounds, heavier guitar riffs, bombastic drumming and louder vocals. This sound created the basis for hard rock. Early forms of hard rock can be heard in the songs "You Really Got Me" by The Kinks, "Happenings Ten Years Time Ago" by The Yardbirds, "My Generation" and "I Can See for Miles" by The Who.

At the same time, Jimi Hendrix, produced a form of blues-influenced psychedelic rock, which combined elements of jazz, blues and rock and roll, creating a unique genre. He was one of the first guitarists to experiment with new guitar effects like phasing, feedback and distortion, along with Dave Davies of the Kinks, Pete Townshend of The Who, Eric Clapton of Cream, and Jeff Beck of the Yardbirds.

Hard rock emerged with British groups of the late-1960s, such as Led Zeppelin who mixed the music of early British rock bands with a more hard-edged form of blues rock and acid rock. Deep Purple helped pioneer the hard rock genre with the albums Shades of Deep Purple (1968), The Book of Taliesyn (1968), and Deep Purple (1969), but they made their big break with their fourth and distinctively heavier album, In Rock (1970). Led Zeppelin's eponymous first album, Led Zeppelin (1969), and The Who's Live at Leeds (1970), are examples of music from the beginning of the hard rock genre. The blues origins of the albums are clear, and a few songs by well-known blues artists are adapted or covered within them.