I’ve never been to Sweden, but I’ve been outside it, hence feel more than qualified to comment on the Swedish Outsiders festival lovingly curated by No Signal. Over two days, and two venues, a diverse cross-section of that most democratic country’s experimental musicians are assembled in London; we’d arranged for the weather to turn significantly colder to make them feel at home. The first day, at the ICA, was a cracker.

First up, Tape gave a performance of quiet restraint that they were in danger of being drowned out by the noise of all the latecomers scrabbling around to find seats (lock them out, I say). The three-piece were presenting the gentle acoustics and electronics of idyllic new album Luminarium, including two of its melodic highlights, “Beams” and “Reperto”. Slow-paced, and highly economical with notes, they were very much the calm before the storm.

That storm soon arrived in the form of BJ Nilsen. I’m a huge fan of Benny’s, but tonight he completely excelled himself with a wholly-improvised maelstrom of sound which had the more delicate members of the audience scurrying for the exits or jamming their fingers in their ears (see picture above). Beginning with squawking gulls - reminding me of his collaboration with Chris Watson - and a chorus of chiming clocks, he began to pile on layers of noise. It began with rumbling drones and some industrial drilling, before adding in some piercing high frequencies. Just when you thought it couldn’t get any more intense it would do just that, and at its apex the space provided by the ICA’s theatre was full: the low notes buffeted our seats at the bottom, while the higher notes were dancing around the ceiling like birds. He collapsed it all back down again to leave just waves: of both the sea and sine variety. There was even time for another brief crescendo of churchy drone, before this extraordinary set ended amongst laptop glitch, and then a hearty ovation from the majority who had remained riveted in their seats.

Folke Rabe is a Swedish avant-garde composer who studied under Ligeti, and who has been championed in recent years by Jim O’Rourke. He wasn’t here to perform as such, instead for the next forty-five minutes we sat in a darkened room and listened to three of his recordings. The first, “ARGH” brought a smile to my face, a collage made from cuts of US commercial radio, with jabbering DJs talking over record intros, and an over-enthusiastic Beatles fan. After this, the empty spaces of the second piece felt dark and pessimistic. The highlight was to be the third, his seminal “What??” – six tones dragged out for twenty-five blissful minutes, imperceptibly shifting from one to another amongst lush pulsing harmonic overtones. Its influence on pieces like O’Rourke’s I’m Happy And I’m Singing And A 1,2,3,4 was clear.

Without a pause for breath, Evan Parker and Mats Gustafsson were on stage. Gustafsson is another long-standing favourite of this site, and he performed here in typically muscular fashion, spitting and growling and rasping, playing the saxophone with his entire body – at one point he was contorted on the floor with the bell pressed against his inner thigh. Evan Parker shimmied around and between this barrage with a long, flowing tumble of notes.

They were then joined by (some others from outside Sweden) Roger Turner on drums, and Pat Thomas on, well, “stuff”. I’ve come across Turner before, but thankfully never in a dark alley - he both looks and drums like a mean motherfucker. His seems to be a never-ending quest to find the sound that fits – is it scraping the cymbal against the snare? No, how about if covering the drums in bits of metal and…no, that isn’t it. How about spinning the cymbal, or using these little sticks, or I have some bells somewhere or…you get the picture. Excellent and very entertaining. Pat Thomas was a terrific foil for the group, backing them up with tapes, loops, drones and the occasional foray into Sun Ra spacey keyboards. Gustafsson ran amok with an array of unusual horns, and joined in a ecstatic hard-blowing middle section with a firey Parker. This was a thrilling end to what had already been a memorable first night; more follows tonight at Café Oto in Dalston.