Today sometimes also referred to as 'urban' music, R&B was originally a euphemistic way of referring to the boogie woogie blues-based music of African-Americans in the 40s and 50s. In some circles, these would be referred to as 'race records.' When white musicians like Elvis Presley began recording these songs, the term Rock and Roll was coined. This transition would not render the R&B genre moot, but would instead apply it to most music made by African-Americans. Over the years, this would come to serve as a Billboard Chart classification for forms such as Soul, Funk, Disco and many modes of Hip Hop. Quite in fact, today, R&B may be said to be the dominant form in popular music once again, with its permeation of the variant of popular forms impacting the sound of music today in the same way that rock would for decades. Particularly in the type of Hip Hop and Rap music which have achieved mainstream popularity, the vocal histrionics, club beats and slick arrangements that are omnipresent may be said to be characteristics of R&B. This genrification is of course made with no small recognition of the way that pop music markets are segmented by race.

Hard Rock also reinforces this notion by catering with almost total uniformity that musical and cultural interests of white males. In all cases, these are not hard and fast...

Hard Rock is a variation on rock music that generally features edgier, louder or more aggressive modes of presentation. This offshoot would probably begin in earnest with the heavily psychedelic and acid rock experimentation of Led Zeppelin, Black Sabbath, Iron Butterfly and Jimi Hendrix. These musicians would rewrite the rules on that which could be considered musically appealing, allowing the volume and aggression to come out on recording. Thereafter, standard Hard Rock would be characterized in the hard drum beats, leading guitar riffs and standard 3 to 5 piece bands of AC/DC, Aerosmith and Guns 'N Roses.
This would produce its own endless array of categories, with metal probably functioning as the most noted, important and frequently reviled. The quintessential Metal bands are Motorhead and Metallica, bands that would make an art of heightening the speed, volume and layering of guitar. Snarling or shrieking vocals are also prominent in this genre. Another very important element of Hard would be punk music, a genre which would proceed from the philosophy that simplicity and aggression were the only ways to return music to its purest roots. This minimalism would also become an important element of this subgenre.