"I wanna see all my friends at once”. That line, from the 1981 song "Go Bang" by Arthur Russell’s Dinosaur L, has always been less a quote than a manifesto at Optimo – a perfect expression of the family atmosphere Twitch and Wilkes’ unique Sunday-nighter managed to foster over 13 years, that just happens to be taken from one of its all-time classic tracks. The words may never have had as much relevance as on Sunday at Optimo’s 20th-birthday festival at Glasgow’s SWG3, and a giant neon sign bearing them welcomed the 2500 well-acquainted Glaswegians who gathered to celebrate.

I arrived a couple of hours after the event’s 2pm opening, and for the first little while found seeing all my friends at once a touch overwhelming – a sentiment echoed by dozens of others I failed to sneak past, and who failed to sneak past me. As the day settled into a rhythm though, and as an unspoken mass accord was reached to suspend usual stop-and-chat rules for one night only to allow visits to the bar and the bathroom to progress unimpeded, it eventually became a touching delight to have so many familiar faces under one roof.

The National:

One of the lesser discussed strengths of Optimo is their knack for carrying off ambitious set-piece events without a hitch. The level of expectation resting on 2010’s Optimogeddon, for example – the last of the pair’s weekly Sunday-night parties at the Sub Club – should have been impossible to meet. Instead it was exceeded by several times, as a step back in time to the full seven-hour feast confirms. Other big moments in Optimo’s history – the dizzyingly high-concept Apocalypse Optimo, a couple of boat parties, a barn dance and live shows from LCD Soundsystem, Liquid Liquid and James Chance & The Contortions spring to mind – have gone off in notably smooth style too, but Sunday was possibly the biggest triumph of all. A year or more’s work had gone into the thing, and 20 artists from around the world booked. A common opinion in its immediate aftermath was that Optimo 20 had gone so well that an annual event should be made of it, though whether Twitch and Wilkes are willing to take on that organisational burden remains to be seen.

Optimo 20 went down over two large rooms within the main SWG3 complex (the Galvanizers, a huge area and the de facto “main” stage, and the smaller TV Studio, which was almost exclusively given over to live acts), plus the 120-capacity Poetry Club. The Poetry Club is where the Optimo-affiliated So Low night is held, and is a contender for the city’s best clubbing space. I dove in there as soon as I arrived to find Copenhagen’s all-girl Apeiron Crew banging out their signature brand of riotous techno and breaks (DJ Normal 4’s "Transcendental Training Tactic" and Schacke’s "Make Them Remember" hit particularly hard) while also having their signature enormous amount of fun together in the tiny DJ booth. Glasgow pair Happy Meals were meanwhile playing one of the most talked-about sets of the day through in the Galvanizers, and taking in a bit of their atmosphere-laden, vocals-heavy live show right after Apeiron Crew proved an enjoyable primer for the breadth of styles on offer at Optimo 20.

The National:

Several of the day’s best moments came in the Poetry Club. Though I missed Aurora Halal’s much-vaunted live show there, I had a great time watching the following set. Ben UFO, one of the world’s finest DJs and a big draw wherever he goes, was wonderfully out of context in such a small space but seemed to revel in the incongruity of it all, and anyone who had elbows sharp enough to get over the threshold and carve out a few inches of dancing space was richly rewarded. It turned out that that group included Ben UFO’s own mother, who danced at the front throughout. It was that sort of day.

At the live stage, Ghana’s King Ayisoba were wonderful value. With at least half a dozen band members on stage at all times, they added a different dimension to an event unsurprisingly light on full-band setups. Back in the Galvanizers, everyone playing was in the mood to let their hair down. Avalon Emerson revisited several cuts from she and Courtesy’s extraordinary, much-talked-about b2b set at Sonar, while the parts I saw of Midland’s two-and-a-half-hour show allowed scant time to draw breath or stop grinning. During the last hour it was sad to eschew The Bug and Miss L’s bowel-trembling bass assault and errorsmith’s intricate, percussive live show in the other rooms, but Optimo’s b2b with The Black Madonna was, realistically, the only game in town.

The National:

Optimo have always revelled in putting new spins on the classics, and the likes of “Go Bang”, Cerrone’s “Supernature”, Hercules & Love Affair’s “Blind” and Zombie Nation’s “Kernkraft 400” were among the Sunday-night standards passed through the macerator, an irresistible bassline or synth riff added here, an explosive drum pattern or second vocal added there. The best of these reworks gave the night its first big finale, a plaintive yet euphoric a capella version of Bronski Beat’s “Small Town Boy”  intermingling beautifully with sampled vocal snippets from Whitney Houston’s “I Wanna Dance With Somebody”. The night’s second big finish followed immediately, as Liquid Liquid’s Sal P, fresh from playing a sax-heavy DJ set earlier in the day, took to the stage to sing “Optimo”, the chaotic, cowbell-driven no-wave track by his old band Liquid Liquid that started it all. The Black Madonna filmed on an iPhone with a sparkly cover, while Twitch and Wilkes sat back and beamed at the sight of a couple of thousand of their friends singing and dancing along, all at once.

Photographs: King Ayisoba, Midland, Sal P of Liquid Liquid: Niall M Walker