Soft rock, hard rock and early heavy metal

From the late 1960s it became common to divide mainstream rock music into soft and hard rock. Soft rock was often derived from folk rock, using acoustic instruments and putting more emphasis on melody and harmonies. Major artists included Carole King, Cat Stevens andJames Taylor. It reached its commercial peak in the mid- to late '70s with acts like Billy Joel, America and the reformed Fleetwood Mac, whose Rumours (1977) was the best selling album of the decade. In contrast, hard rock was more often derived from blues-rock and was played louder and with more intensity. It often emphasised the electric guitar, both as a rhythm instrument using simple repetitive riffs and as a solo lead instrument, and was more likely to be used with distortion and other effects. Key acts included British Invasion bands like The Who and The Kinks, as well as psychedelic era performers like Cream, Jimi Hendrix and The Jeff Beck Group. Hard rock-influenced bands that enjoyed international success in the later 1970s included Queen, Thin Lizzy, Aerosmith and AC/DC.

From the late 1960s the term heavy metal began to be used to describe some hard rock played with even more volume and intensity, first as an adjective and by the early 1970s as a noun. The term was first used in music in Steppenwolf's "Born to be Wild" (1967) and began to be associated with pioneer bands like Boston's Blue Cheer and Michigan's Grand Funk Railroad. By 1970 three key British bands had developed the characteristic sounds and styles which would help shape the sub-genre. Led Zeppelin added elements of fantasy to their riff laden blues-rock, Deep Purple brought in symphonic and medieval interests from their progressive rock phrase and Black Sabbath introduced facets of the gothic and modal harmony, helping to produce a "darker" sound. These elements were taken up by a "second generation" of heavy metal bands into the late 1970s, including: Judas Priest, UFO, Motörhead andRainbow from Britain; Kiss, Ted Nugent, and Blue Öyster Cult from the US; Rush from Canada and Scorpions from Germany, all marking the expansion in popularity of the sub-genre. Despite a lack of airplay and very little presence on the singles charts, late-1970s heavy metal built a considerable following, particularly among adolescent working-class males in North America and Europe.

From Wikipedia