It's hard to think of trip-hop without considering the history of the (contemporaneous) electronic music. I don't intend to write down a book in here. Neither want I to be a theoric. I just intend to contribute a bit, if I can, to the understanding. Thus I'll try to be the most objective and succinct as I can. Due to that I apologize. Maybe this is gonna be the shortest and most subtle text you'll ever read about this topic.

In the beginning of the 80s, more specifically around Chicago, Detroit and New York (USA), some musicians had the idea of re-making the disco music of the 70s electronically, infusing influences such as funk, soul and r&b (DJ Frankie Knuckles and Tony Humphries aren important names to be considered on that). They've created what we know as house music — term created as an abbreviation of "Warehouse", a club in Chicago where Knuckles played between '77 and '83, making the first experiences with the style and thus starting what soon would be called by the name of that club: warehouse music, and later just house.

During the decade, many DJs started making experiences with it, generally speeding up the bpm (beats per minute); then reducing or even cutting off the melodic side of it and attributing a big importance to the beats  —  we have techno; mixing it with classic music (in the very beginning) and attributing a major importance to the melodic part — trance was made up; or changing the rpm to up and using the pitch to slow it down again, among other experimentations as speeding up hip hop beats and using reggae bass lines, on such a way to develop broken beats to loop on a typical atmosphere — drum n' bass and other specific breakbeat variants.

Still in the beginning of the 80s, some brilliant guys realized it was not necessary to put the music just into upbeat. It could be also downbeat (generally and second a classic point of view, under 120 bpm). Thus, in Bristol (UK), a crew named The Wild Bunch * started producing music on that direction. After all they've made up trip-hop **. From that crew Tricky, Mushroom, 3D and Daddy G have come. In 1991 they released Blue Lines, under the name of Massive Attack, the first album of the genre.  Massive has brought the electronic side of trip-hop, as well as reggae and hip hop influences; Tricky, originally from Massive and right after a solo artist, contributed on the hip hop influenced side of the genre. Smith and Mighty were also involved with the project since the very beginning, and were putting out the reggae infused side of trip hop. Sometime later Portishead has come up, bringing with it jazz influences. DJ Shadow, at his turn, has influenced the instrumental side of the genre, with his great job at the turntables. Other names to be considered are Monk & Canatella, with their melancholic guitars and a rock influence.

Even being very short and simplistic and exactly for that possibly full of banalizations, I think it's worth to have at least that tiny story on mind. It can be helpful, a minimum, to understand the genre.

* to read a bit more about Wild Bunch, check their profile at  this website.

** The term "trip-hop" came around only in the mid-90s, originally used by the british magazine Mixmag as an attempt to define the album Maxinquaye of Tricky; the term got popularity with time, becoming usual among listeners, media and even the music industry.