Short answers, pulled from the story.
Hard rock is a form of loud, aggressive rock music that functions as both a rhythm instrument using repetitive riffs and as a solo lead instrument. The electric guitar is often emphasised and used with distortion and other effects to create this sound.
The genre began in the mid-1960s with garage, psychedelic and blues rock movements. Some of the earliest hard rock music was produced by the Kinks, the Who, and the Yardbirds.
Led Zeppelin mixed early rock band music with a hard-edged form of blues rock on albums like Led Zeppelin II in 1969. Deep Purple achieved commercial breakthrough with their fourth album Deep Purple in Rock in 1970 while Black Sabbath released Paranoid in 1970.
The 2000s saw renewed interest in established bands attempts at revival and new hard rock bands. Reunions occurred from Van Halen in 2004 and then Roth in 2007 and the Who delayed until 2006.
Vocals are often growling, raspy, or involve screaming or wailing that can appear in a high range or even as falsetto voice. Drumming characteristically focuses on driving rhythms with a strong bass drum and sometimes uses cymbals for emphasis on the snare backbeat.