Brian Eno - Pure Scenius, The Dome, Brighton

It's 4.00 in the afternoon and Brighton Festival curator Brian Eno is fast-forwarding us to the future. Perched onstage behind an array of consoles, he tells us we're in for "something special for the end of term". The conceit is that the audience are students in the year 2069, indeed the event programme takes the form of notes for a university course on "Cultural Reconstructions". Rather than a single "lecture", though, there are three, and they will take us through to 11.00 tonight.

Eno tells us before he begins that "after the Great Pulse of 2042" all digital recordings of the early 21st century have been lost so he and fellow "professors" will be recreating sounds from long-gone music scenes based on descriptive writing surviving from the period.

Scattered round the stage are his assistants in this enterprise, Australian avant-jazz trio The Necks (a drummer, a pianist and a double bassist), guitarist Leo Abrahams, electronic wizard Jon Hopkins and "ethnic linguistics specialist" Karl Hyde (frontman of techno act Underworld). They will, Eno explains, kick off with "a bit of ambient thrash lounge". This turns out to be floaty soundscaping with Hyde's airy vocals leaning into David Sylvian territory until a welter of tribal percussion kick-starts his trademark rhythmic bark for a prolonged concoction midway between Underworld and Bow Wow Wow.

The sounds of drills, buses and machinery are manipulated into crunching rhythms

Eno then lectures for a bit about categories of painting to a drifting sonic landscape before announcing we're in for some "Niigata machine techno, a very popular form for a few years", whereupon the sounds of drills, buses and machinery are manipulated into crunching rhythms by Jon Hopkins. These sections turn out to be some of the day's best. I'm keen to go on Eno's sci-fi adventure, wallow in his conceptual artifice, so when the sounds push at the boundaries of the usual, all is well. When they settle down to more recognisable improvisational techniques, however, my suspension of disbelief fractures.

Next on the agenda is a piece for two pianos, one slowly replicating and building on the simple motifs of the other. Later I found that many of the audience thought it both clever and beautiful, but my mind drifted off into mundane domestic shop-keeping until waves of didgeridoo-like noise woke me up.

Eno then told us that the band had written one actual song, "Pink Moon", and suddenly his experience working with U2 and Coldplay came into focus. It was a delicious melding of country and jazz featuring an evolving harmonic structure and epic quality that shouted for stadium rock performance, before eventually descending into a hypnotic drone. With that, "lecture one" was over, although Eno did allow us a brief burst of the "Ikebana Noise Club sounds of 2025" before he disappeared.

Between "lectures" there's an hour-long break. Time to grab a quick bite to eat but surely the whole thing would have kept its momentum and conceptual solidarity better with pauses of 15 minutes or less. That would have put both audience and band on a more immersive, if exhausting, mission.

At 6.30pm things begin again. The 2069 routine is drilled into new arrivals and we're off with a dose of "North American Pedagogic" which, Eno explains, was the music used to accompany lectures before the advent of "pharmaceutical learning". To illustrate, he holds forth about Cezanne while the band plays a faintly dissonant extended abstraction. Every now and then players slope off to stage-set sofas - a kind of subs bench - to chill out, eat fruit and have a sip of water, physically emphasising that not everyone has to play all the time.

As the evening wears on, Karl Hyde becomes a mixed blessing. He's well-suited to pile-driving beats and even the occasional exercises in breathy vocalising, but when he's required to emote theatrically in other styles, all drawing on his stream-of-consciousness wordplay, there's something a little awkward and forced about his manner. In any case, his extended presence in the music reduces its potential, drawing attention to the fact that it's essentially an avant-garde jam band bedding down behind his cyber-beatnik spiel. And another moan, the minimalist duel piano play-off reappears, followed immediately by the lovely "Pink Moon". Tickets were advertised for attendees to come to all three "lectures" (for £55), but moments like this hint at a repeating concert cycle rather than an extended suite. Happily such negative reveries are punctured when an overly refreshed man bursts into the hall and bellows, "Brian, I love you." Eno looks up over his ever-present thin spectacles and says, "I'm very flattered... I'm guessing you have a beard."

The rest of the set is smothered in synthesized beauty and drifts to a close in shimmering soundscapes from the possible future.

Another break, an hour lurking at the bar. I drink wine and mentally will the band to veer towards ad absurdam marginal extremes - gabber, death metal, serialism, Kraut-drones, etc - rather than avant-jazz ambient jamming.

9.00pm, back in the hall and Eno mocks our "tepid applause", albeit as genially as is possible. We're back to 2069, a fact he punches home with mention of an alternate college course on "trance finance - dance to get rich" which causes a welcome round of chuckles. Then it's more "American Pedagogic" during which Eno fascinatingly ponders the ideas of American art theorist Arthur Danto before the band sweeps off on an elegant baroque orchestration that ends with Necks pianist Chris Abrahams playing his instrument with balled fists.

Is it the amount of time I've been here, the repetition of certain material or the woman behind me sniping loudly and unremittingly about Karl Hyde? Whichever option, the pleasurable momentum of the day fades somewhat during the latter half of this third "lecture". It doesn't help when Hyde's studied theatrical voice crops up for a poetry duet with Eno that keeps returning portentously to the phrase "What if", and then the bloody one note piano thing comes back again, followed by a Necks/Hyde jazz odyssey which is weirdly and unfortunately redolent of Black's irritating 1987 hit "Wonderful Life". Then, just at the finishing post, they pull out a banging number called "I Want to Touch it" which injects a dose of pizzazz as Hyde rises from the laptop, behind which he's been sitting the whole evening, and jigs over to the drum kit for a smidgeon of hip-wiggling as he fires out his lines.

"We weren't prepared for an encore," Eno tells us, "we only wrote six hours of material - do you want our one song or something else?" "Something else!" shout back a handful of voices. Eno rolls up his sleeves. Time to get serious. "Music is normally about love," he says, "but this song is about capital assets management." It gets a laugh and the piece in question is a squelching dub that eventually emanates unlikely psalmic qualities. With that the band take their bow and I'm spat out of the time portal back to the bustling streets of Brighton 2010, chewing over an evening that was by turns dynamic, frustrating, funny, ponderous and intellectually playful. If nothing else, Pure Scenius has left me eager to pop forward a few decades and attend an evening class in the "Vaxhelian Breath Languages" mentioned in the programme notes...

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