A NOTE ON TERMINOLOGY
Whereas the term "hip hop" refers to both instrumental music and some types of music that contain rapping, "rap music" refers mainly to hip hop music with rapping in it. Not all music that has rapping in it, however, is actually rap music, and not all hip hop music has rapping in it, see records by the Planet Patrol or Pretty Tony. "Hip hop" also refers to non-musical aspects of this cultural movement, e.g. breakdancing and graffiti.
The History of Hip Hop/Rap
The roots of rap music are West African. The griots of West Africa are the forefathers of rap music. It is said that the Jamaican Kool DJ Herc first tried to popularize reggae music in the Bronx, NY. Later on, he switched to funk records but remained true to the Jamaican art of "toasting" or "dee jaying", which became known in hip hop as "rapping".
Initially, Herc was trying out his reggae records but since they failed to cut ice he switched to a Latin-tinged funk, just playing the fragments that were popular with the dancers and ignoring the rest of the track. The most popular part was usually the percussion break. (Toop, Rap Attack 2, London: Serpent's Tail, 1991; p. 60)
These breaks were artifically prolonged, and mixing techniques as well as scratching developed along with the breaks. There are, of course, also other influences that lead to the genesis of modern hip hop. On the one hand, the rich (US) African American tradition with radio DJ's, artists such as James Brown, Lightnin' Rod and the Last Poets as well as Gil Scott Heron.
As Kool DJ Herc suggests, also white people were involved in hip hop from the start. But next to Black people, Puerto Ricans were the driving force behind this new musical style. However, a whole decade passed until bilingual raps started appearing, see Latin rap.
The first rap records were actually recorded by live musicians in the studio, with the rappers later on adding their vocals. This changed with DJ records such as Grandmaster Flash's "Adventures on the wheels of steel" as well as new, electronic recordings such as "Planet Rock" by Afrika Bambaataa and Run DMC's very basic, all electronic "Sucker MC's" and "Peter Piper" which contains genuine cutting by Run DMC member Jam Master Jay.
While Run DMC laid groundwork for hardcore rap, "Planet Rock" was the first electro funk track. This highly influential piece of music lead to a wave of electronic pop, known as freestyle, "Latin freestyle" or "Latin hip hop", as well as countless electro funk records in NY, LA (Egyptian Lover) and Miami (Pretty Tony). In Miami, a new bass-heavy style developed, it was called "Miami Bass" in the beginning and is now known as Bass or "Booty Bass". It was designed to demonstrate the strength of the stereo systems of cars and is basically dance music. Some Latin artists also embraced this new style. Also, Kid Rock.
Brother D was the first rapper to talk about political issues, Grandmaster Flash and the Furious Five followed with their own "message rap", called "The Message", in 1982. In 1987, Public Enemy brought out their debut album on Def Jam - one of rap music's most important labels - , and Boogie Down Productions followed up in 1988 with "By all means necessary" - probably the first "conscious" rap albums.
Influenced by the track "PSK - What does it mean" by Philadelphia's Schoolly D, west coast rapper Ice T, created his own brand of crime rhyme that was popularized especially by NWA and became known as Gangsta rap. In the 1990s, the music became softer, influenced by former NWA member, Dr. Dre's Album "The Chronic".