There's classical music, and there's pop. You can throw as many violins into the bridge section as you like, and you can amplify the orchestra all you want as well. It's unfortunate, but a certain divide looks set to stay. However, we were given a glimpse of a better world on Saturday night with the London Contemporary Orchestra, who somehow succeeded in filling the Camden Roundhouse with keen, engaged listeners drinking Becks, for a cutting-edge Reverb Festival concert which included works by arch-modernists Xenakis and Stockhausen.

The best thing about this was that it wasn't some sort of stealth education scheme, an insidious effort to force Culture on Youth. Saturday evening was about new classical music actually being cool. Like all evenings put on by the record label and music promoters Nonclassical, the concert was arranged in three shortish sections, punctuated by brief DJ sets in the bar. Before and after the main show there was more live music in the bar too, which ranged from a solo set on bass clarinet by Scott Lygate to a piece for two Nigerian Fanta bottles played by Joby Burgess.

As well as the Xenakis and Stockhausen, the concert featured Orion by the mysterious Canadian composer Claude Vivier (1948-83), and two pieces more than worthy of their own headlines: a Concerto for Bass Drum and Orchestra by Nonclassical founder Gabriel Prokofiev, and Doghouse by Jonny Greenwood, who is also a guitarist in Radiohead. From the evening's programme and format alone, it was clear even before it began that this was to be an evening of amazing and often slightly weird diversity, and a brilliantly managed exercise in boundary-smashing.

The LCO, conducted by Hugh Brunt, were on great form right from the opening. Iannis Xenakis' Metastasis is a beautiful effect-piece which begins with a dense, piercing plateau of strings, and the orchestra pulled this off faultlessly. For all the piece's rigour and constructedness, at its core is something very touching, and the orchestra's sensitive reading made it sound slightly like a robot crying. Maybe less emotive was Stockhausen's Studie I, a solely electronic piece for which the lights were dimmed – but this was still an enthralling listen and a wonderful use of the massive, resonant Roundhouse space.

Gabriel Prokofiev's Concerto for Bass Drum was receiving its first European performance, and Joby Burgess gave it a great airing, playing with excellent control and extracting a huge range of sounds from the drum. There were crazy effects galore, from bowing a string protruding from the middle of the drum to tapping on its metal frame with (what may have been) thimbles. The virtuosity made for an enjoyable performance, but the composition had perhaps less of a rhythmic edge than I had expected; this was not a concerto for the throbbing bass drum of dance music, but a moderately serious work which integrated elements of dance music into the orchestral part as much as into the solo one. A fascinating experiment, but not quite what it might have been.

Prokofiev's undoubted compositional inventiveness could perhaps have been extended to his orchestration as well, which was quite square at times – and this problem only felt more acute on hearing the exquisitely arranged Jonny Greenwood piece which was up next. With a subtlety and colour to its orchestration to make Ravel blush, Doghouse has a passion, sincerity and clarity quite rare to new classical music. It was structurally very free, but there seemed more than a hint of inspiration behind its sudden changes of path. Underpinned by a string trio of Daniel Pioro, Robert Ames and Oliver Coates, the LCO's strings shone particularly bright once again.

Can you have opposite ends of a cutting edge? If so, Prokofiev and Greenwood may be situated there, the former looking towards the popular from a classical basis, and the latter having moved the other way. It's a simplistic binary, but an interesting one, which Saturday's concert highlighted. Both composers, though, doubtless deserve huge praise for their recent strides in music, even if on this occasion it's Greenwood who takes the prize. Just as Prokofiev should be taken seriously on his own terms, and not those dictated by the fame of his illustrious grandfather, so Greenwood should be treated in the same way as any other emerging composer, despite his unusual background. I am definitely intrigued, though, as to what would happen if a few more composers spent a decade in one of the world's most successful rock bands before turning to 'classical' composition.

Claude Vivier's Orion was an intense end to the more formal part of the evening, with the orchestra playing in a wash of red light. This serious, slightly meandering composition was not convincing me until two completely foreign notes appeared, about half-way through, as if from nowhere. From then on I was gripped, completely caught up in its complexities, and there was much to discuss as we made our way out to the bar.