The scene was driven around the M25 motorway (London's orbital motorway), and its audience was mainly urban teenagers and lower middle-class suburban teenagers with cars. The audience was very much multicultural, with black, white and Asian influences resulting in a unique sound. The scene expanded rapidly in 1991, with large raves of 30–50,000 people attending in open air venues around England, put on by Spiral Tribe and other free party sound systems held at locations up and down the length of England. The late 1980s house music raves such as Sunrise UK spawned the idea of holding huge parties rather than hosting more intimate parties at small clubs. The breakbeat hardcore raves modeled their events after these early raves.
In the early years, the underground sound became more mainstream. Even without radio play, many hybrid and regional styles made their way into Top 20 charts. However, during the early 1990s, the two main subdivisions of this underground rave movement were primarily either a. House & Techno (often used interchangeably or vaguely used to define a multitude of sub-genres of house music) and b. Breakbeat Hardcore. Approximately in 1993, the scene fragmented (a. & b.), and forked off into two distinct styles—jungle music (later giving rise to drum and bass) and 4-beat (alternatively known as happy hardcore). This split was evident at the early Roast events. Roast was England's largest most respected original jungle promoter. The promoters of Roast referred to it as the house scene branching off and going in their own direction, not accepting the new jungle sound (which largely dropped the 4-on-the-floor house kick drum). Jungle's sound was more focused on basslines, often with jazz-like undertones, while 4-beat retained the rave synths, the 4/4 kickdrum and happier piano elements. By 1996, most 4-beat had dropped its breakbeats (in part due to bouncy techno), while drum and bass had long dropped the techno style synth stabs, further separating the two styles. The almost independent evolution of styles created distinct sounds of "bleep and bass", brutalist techno, hardcore jungle, pop-rave, UK garage, and ragga-techno sounds.