It's 9:36pm, Friday. I'm stood looking at the semi-illuminated face of a building wondering if what I'm seeing is real. It's cold. In just a few hours the pavements will be coated with frost and right now the temperature is dropping rapidly. I should get moving, it's going to take me another twenty or so minutes of walking to reach De Helling where in just a few minutes Lee Ranaldo & El Rayo will take to the stage, but I keep staring. I take out my phone. Tomorrow morning I'll confirm that I really did see a UFO balancing on the edge of a government building in Utrecht.

I'd been in Utrecht for only two days and already Le Guess Who's mix of heady, experimental fare had taken ahold of my senses. Over the course of my weekend in the Dutch city I saw spaced-out soul, absorbed anxious waves of ambience and been pulverised by violent electronics. Most festivals are described as being like nowhere else on earth, but at Le Guess Who?, alternate states and ways of being feel legitimately possible.

Thursday

Much of the focus during Le Guess Who? is on Tivoli-Vredenburg, the city's central performance space. This labyrinthine building feels purpose-built for an event like this as its numerous sub-venues allowing audiences to quickly move between the main stages and sample a much wider variety of music. There's rarely a break in the music, as one act ending is simply a signal to move on to another space. This helps encourage exploration, both spatially and musically, as you're never without options should something fail to capture your attention.

By comparison De Helling, a more traditional gig venue located near an industrial estate on the outer edge of the city, represents much more of a commitment - especially if you haven't rented a bike. It's a good thirty minute trek, and you can't be guaranteed entry when you get there. I learn about this on Thursday evening as I start to hear reports of the venue hitting capacity ahead of Preoccupations' set. My Thursday evening, however took place entirely within Tivoli Vredenburg - there will be more time to explore the city's other venues over the coming days.

Thursday starts off strong with William Tyler opening the festival in Grote Zaal. Alone on stage, he moves from finger-picked acoustic guitar to soaring shoe gaze loops, lulling the assembled crowd in rapturous silence. His music feels a little more bittersweet than usual, and as he talks about his experiences of the differences between rural America and the cities, it becomes clear as to why.

Later that evening Bassekou Kouyaté & Ngoni Ba turn Grote Zaal into a frenetic dance party as the family blast through an energetic and somewhat hypnotic set. Down the front kids are going wild, throwing themselves about as though they were listening to EDM. Things mellow down as Kouyaté plays an old 17th century song he explains was once reserved for royalty. "Tonight," he tells the crowd, "you are the kings and queens."

The first surprise of the festival is found in the spaced-out soul of Lonnie Holley. The visual artist, turned performer leads us through an improvisational set, with his warm vocals drawing the audience in. Down front a couple sit cross-legged on the floor, their eyes closed, and swaying to the swirling keyboard melody. It's so easy to get lost in Holley's sound-world, so much so you never want it to end.

Deerhoof turn in an upbeat, and expectedly kooky performance in Pandora, with drummer Greg Saunier delivering an entertaining education in percussion techniques. After they're finished I race upstairs to Cloud Nine to catch Fennesz. He conjures up a wall of droning guitar loops that is over just a little too soon. But, after finding a spot on the crowded balcony, it still manages to enthral.

My night ends with a pulverising techno set from Kyoka. Her set is at times a little chaotic, even ending abruptly when she thinks she's ran out of time, but it injects new energy into the crowd, sending them into a frenzy of dancing. By 2am my ears are ringing, my body exhausted and I prepare myself to enter the cold for the short walk back to my hotel.

Friday

Domtoren is a 14th century bell tower that towers over the city of Utrecht. It can be seen from almost anywhere, and acts as a useful tool for navigation in the city. Its bells also ring out every 15 minutes, so in a short space of time you get used to the sound of its chimes. The only time this doesn't happen is on Friday and Saturday mornings, where its Carillon bells form the basis of an ongoing 'concert'.

Sat in a small wooden room at the top of the tower, Malgosia Fiebig plays the bells following a tradition that stretches back centuries. She mainly plays arrangements of pop music, using the very public nature of her performance as a way to comment on events. This morning she begins her one hour concert by playing a trio of Leonard Cohen tracks in honour of the late artist's passing.

Friday is where Le Guess Who? really kicks things up a notch. The number of venues available to audiences almost doubles and for those that want to make the most of the shows outside of Tivoli-Vredenburg, a bicycle is a necessity. As I make my way to De Helling later that evening, I will come to regret the fact that I didn't hire a bike. I start my evening, however, back in Pandora watching the gnarled, apocalyptic blues of Duke Garwood.

The first real treat of the evening comes in the form of a superb set from composer Jherek Bischoff. Leading a string quartet - and accompanying them on bass, percussion and piano as necessary - he takes the audience at Hertz on a journey through his compositional work. As well as renditions of tracks from Composed and Cistern, his two solo LPs, we also get covers of tracks by Kronos Quartet, Konomo no.1 and David Bowie. I had worried that Cistern's slow, reverb heavy sound wouldn't translate well to a live environment, but the hushed audience and some sound mixing wizardry helps to convey the often tense and claustrophobic nature of the work.

I manage to catch Hannah Peel's wonderful electronica in Cloud Nine - at times I'm reminded of East India Youth's more lyrical tracks - before leaving Tivoli-Vredenburg for De Helling. The venue is much quieter this evening, with the small venue about half full. Lee Ranaldo & El Rayo are already on stage when I arrive, tearing through a set of all new tunes (plus an exhilarating cover of Lou Reed's 'The Ocean'). The tracks, which Ranaldo has written with novelist Jonathan Lethem, are as lyrically dense as you'd expect and the set certainly whets the appetite for the band's forthcoming LP.

Ranaldo's set is followed by Klara Lewis, in perhaps the only moment at Le Guess Who? where a stage line-up feels a little mismatched. Whilst Ranaldo specialises in grungy alt-rock, Lewis brings dark, physical electronica with trippy visual accompaniments. There's little dancing for Lewis' set, with many members of the audience taking a seat on the floor to simply let the waves of glitchy percussion and synths to be absorbed into them. I feel myself slipping away during the set and, once it's over, stumble out of De Helling to wander the streets back to Tivoli-Vredenburg.

Saturday

Le Mini Who? is a free offshoot of the larger festival which sees local coffee shops, record stores and venues play host to acts from the Dutch underground. Starting at 2pm and running throughout the rest of the day, it turns Saturday into a test of endurance if you really want to sample everything Utrecht has to offer this weekend. It also reveals a whole new side to the city as familiar locations such as Village Coffee (a spot I'd been regularly hitting up each morning) are twisted into sweaty, raucous gig venues. Or at least that's what happens when shambolic punk act Charlie & The Lesbians take over the space, their shirtless lead singer screaming in the faces of the crowd as he wraps himself in a microphone cable.

Elsewhere, Crying Boys Cafe bring tropical 80s pop (and their own palm-tree) to the ACU, a former anarchic squat, turned volunteer bar and live venue. Whilst over at Tilt! Kanipchen-Fit bring a heavy dose of righteous soul rock.

Saturday evening is the first time I find myself getting turned away from one of the main shows. I'm in line for Circuits Des Yeux at Janskerk, a beautiful church located not too far from ACU, when I hear that it's at capacity and a one-in-one-out policy is in effect. I accept my losses and head to Tivoli-Vredenburg, for Ryley Walker's dreamy 70s-esque pop in Pandora.

This is followed by Julia Holter, the only one of the four curators I manage to see live. Holter is as wonderful and mesmerising as ever, leading her band through a set that pulls from all four of her albums. Unfortunately, the crowd seems to thin during a double header of Ekstasis and Tragedy tracks, but it's hard to tell if this is due to the material, or the fact that Dinosaur Jr. are about to take the stage. I suspect the latter as, when I reach Ronda, the venue is full and I can only manage to poke my head around the door.

I settle instead for catching Cate Le Bon at Pandora. She's also drawn a sizeable crowd, so I have to settle for a restricted view from one of the balconies. Despite that her performance is fantastic and I allow myself a moment to relax. This is followed by another trip to Cloud Nine for Jackie Lynn, the electro-country alias of Circuit Des Yeux's Haley Fohr. Hidden from view by a sheet, our only glimpse of Lynn is the unmistakable silhouette of a country star which is set against projected images of stylised Americana - roadside buildings and the neon lights of a city flashing by. It's an otherworldly performance, with Fohr's voice recalling electro-pioneers like The Knife and Planningtorock and the audio-visual spectacle of the show adding a genuine sense of mystique.

Laurel Halo is up next, delivering an infectious selection of techno, which seemed to pull heavily from recent LP In Situ. Much of that crowd sticks around for RP Boo, the Chicago footwork producer bringing a much more uptempo and uproarious set, but ultimately one that doesn't have quite the same impact for me as Halo's.

Sunday

By now the festival is really taking its toll so I decide, in an effort to rejuvenate mind, body and spirit, to catch Karolus Magnus at Leeuwenbergh. It works. Their performance of Gregorian chants helps to soothe the soul and prepare me for the final day of the festival which, despite it's smaller scale and earlier finish, will prove to be the most eclectic and experimental day yet.

For the early part of the day I spend more time moving between stages only catching portions of bands' sets. It's not that I'm disappointed with what's on offer, just there's a lot that I want to check out before I leave. Phurpa are my first stop, the two Russians on stage evoking the chants and ritual of pre-buddhist tradition. It's part drone, part theatrics, as the two cloaked men growl, play horns and percussion, and blow smoke.

Scott Fagan draws a large crowd for a run through of South Atlantic Blues. His brand of toe-tapping country blues brings a feel-good optimism to the weekend. Anna Von Hauswolff, meanwhile, delivers a truly thrilling set of dark, visceral rock, which could have easily been one of the evening's highlights if it weren't for Patty Waters.

Waters is one of those acts you yearn to see at a festival. An act which knocks you senseless and has you hollering for more, followed by spending your remaining day breathlessly recounting the experience to friends. Waters free jazz was (and still is) full of pain and grief and every word she utters feels like the artist is purging her emotions in real time. Her set includes political piano compositions, covers of Nina Simone and David Bowie, as well as her own material - but every track feels born anew in her presence. Her startling take on Bowie's 'Wild Is The Wind' wrings every last drop of unrequited love out of lyrics and I leave her performance feeling emotionally and physically drained.

I recover with the experimental accordion playing of Pauline Oliveros. Her music is astounding as she squeezes all manner of weird and wonderful sounds out of an accordion and some effects. That's followed by Jerusalem in my Heart, who have constructed a second platform up in Cloud Nine so that Charles-André Coderre can operate a series of film projectors in order to superimpose looping clips and oblique images behind founder and performer Radian Ghazi Moumneh. It's a perfect compliment to Moumneh's emotive performance, in which guitars and voices wail out into darkness.

The festival ends back in Pandora, for a triumphant set from footwork producer JLin. Proving that dance music needs to be felt physically, rather than just listened to, she directs an intense workout during which she rattles through Dark Energy. 'Guantanamo', which opens the set, takes on a new, violent guise as it erupts from the stacked speakers. By this point I'm worn down, ready to turn in before my flight home the next morning, but the sound of 'Erotic Heat' and 'Unknown Tongues' re-energises me one last time. For one more hour, Utrecht is the place to be and I never want to leave.