In London it's 10 AM—Max Richter's least favourite time of day. He likes his sleep, it's his favourite thing to do. So much so, the German-born British composer wrote an eight-hour opus about it. Contrary to how it's being perceived, though, Sleep isn't a sleeping aid. It's a bit more complex than that, the experience of hearing it is as nuanced as the composition itself. It's a huge expanse of music left deliberately open, to be explored and mapped out on one's own. It's big enough to get lost in. It's so big even Richter, in a way, is still figuring it all out.

So far Sleep has only been performed once in its entirety. On September 27th, 2015, from midnight to 8 AM, an audience was invited to camp out with Richter and a troupe of musicians in the reading room of the Welcome Library in London. It was aired on BBC Radio 3, making broadcasting history and setting two Guinness World Records in the process. In March Richter is set to do it again, this time with three overnight concerts in Kraftwerk Berlin as part of Berliner Festspiele's MaerzMusik Festival.

Sleep came out last September through Deutsche Grammophon. There was also a less intimidating CD version, From Sleep, featuring seven song-like offcuts. "Path 5" (from the latter) has since been transformed into stunning remixes by Mogwai and Clark. It's the kind of crossover we've come to expect from Richter, who's also been remixed by the likes of CFCF and Efdemin, and who's famously worked with Roni Size and Future Sound Of London.

But this is just the tip of a very large iceberg. Richter's written countless scores for TV and film, most recently for HBO series The Leftovers. There have been ballet and opera collaborations he's produced with award-winning choreographer and director Wayne McGregor, and plenty of self-initiated projects, like Memoryhouse and The BlueNotebooks, two of Richter’s earliest works, which deployed what has become his trademark style of electronic-meets-traditional forms of classical composition. Ahead of the public premier of Sleep, arguably one of the most provocative pieces of contemporary music out there at the moment, I sat down with Richter in an attempt to figure it all out.

What were the dynamics like during those eight hours?

It was really interesting. Performers are a bit like racehorses: you press "go" and boom, they give a performance. It's a very adrenalin-type situation normally. But this is, in a way, the opposite of that. It was almost like being at home, it felt like a campfire.

How about the audience, how did they respond?

The audience arrived and went to bed, which I thought was great. Obviously that's what the piece was intended for but you never really know with a new project if it's actually going to work the way you think. I thought, well, maybe people would sit there and try to listen all night. But really no one did. People were awake some of the time and asleep some of the time. I'd be playing and look round and there'd be a room full of people just asleep, with the odd bit of snoring.

How did it feel as a performer to subvert audience behaviour like this?

It was like an act of trust from them because going to sleep, you're vulnerable. You don't know what could be happening around you, and it's a room full of people with music. It felt like we'd been entrusted with something.

Did you feel more connected to the audience as a result?

Yeah completely, but in a different way. Live music is all about connection with the audience; it's a dialogue really, we're having a conversation. We've got this thing we're going to play and you get a feeling for how the audience are and what they're thinking, how they're hearing it and how they respond. And all of that was going on, but in a different state.

I tuned into the radio broadcast, but instead of sending me to sleep, it kept me up; I wanted to hear where the piece was going. Have you had similar responses to this?

A lot of people are talking about it like it's a sleep aid, like a big sleeping pill, and it really isn't about that. It's more of an experiment. It's a "what if" project. What if I tried to write a piece of music to accompany sleep? And it's an exploration of hearing and sleeping and music, and how they can all fit together. It's not, "Here's something for insomniacs." It isn't about that. So you staying awake and listening to it, that's just as valid as anything else.

I interpreted the project as something researched-based, a piece that's more about sleep than for sleep. When did you start working with the neuroscientist David Eagleman?

This is one aspect of the project. Having decided to make a piece trying to investigate how sleep and music fit together, I then had to try and get some data on what the sleeping mind actually does, how the senses function when we're sleeping. David is a neuroscientist but he wears two hats: he's a creative fiction writer by day, and a neuroscientist by night, or vice versa. He's an interesting guy. So I consulted with him, and we talked a lot about the way the brain and the mind operate at various different bits of sleep. For some of it you are just checked out, your mind is on holiday; other times the senses are active, information processing is going on, hearing is active, all sorts of stuff like that. I wanted to try and understand it a little bit just to make sure that what I was trying to do creatively and intuitively wouldn't be a misstep.

From my point of view, sleeping and music are both altered states. Intense engagement with a piece of music is a kind of altered reality. Maybe that's just me as a musician talking, but it feels like that, it feels like another mode of being. And sleep is the same, it's another way of being a human being, of experiencing our existence. And that's quite a profound situation. So those two altered states feel like they're related. The lullaby tradition is a human universal. It's in pretty much all cultures. It attests to that, we feel an intuitive connection. So why is that? And that's one of the things I wanted to look at with the project.

What part of your consultations with Eagleman did you apply to Sleep?

The notes that David gave me on the sorts of things which could be useful or complementary to Sleep actually chimed in with what I do musically anyway. There's a bit of sleep called slow-wave sleep, which comes around roughly every 90 minutes, where the mind is processing and restructuring information. It's turning short-term memories into long-term memories and learning. All this kind of organisational stuff happens, and a lot of neuro-rubbish is being thrown out. It's like emptying your trash, organising your desktop. And it turns out you can induce this state with sound; they've been doing various laboratory experiments. And the kind of sounds that help to foster this state are very low-frequency tones and a lot of repeated cyclical patterns. Repeated cyclical patterns and low frequency tones pretty much describes my compositional universe. So I was like, "Great, I can just write the music I write anyway and it's working." It was a happy accident.

What did you ultimately want to achieve?

I wanted to try and get to a situation where that individual person's listening is really at the centre of the piece, rather than it being about my ideas or some text or great concept; where the piece is big enough for somebody to navigate their own way through it and reflect on it while it's actually happening.

I feel like this project foregrounds something that has always been in the background of what I've been doing. If you listen to, say, The Blue Notebooks or Infra or something, they've all got something of that DNA in there.

Has the project changed you in any way or caused you to readdress certain things about yourself and your work?

I think all projects do. You're making choices, and then you wonder why you've made those choices. And certainly it's clarified—again speaking personally—my relationship to this whole data universe. Stuff happens, you live your life, and it's a bit unreflective most of the time. We manage stuff, we're firefighting data, but we're not really aware of it because it didn't happen all at once. It just crept up on us. But this project has made me reflect on that, and how I actually want to spend my time. Normally when I am working on a project, I'm thinking about music. I'm thinking about the way the notes fit together and the sounds and the recording and the tape. But this has been a little different, it's more to do with how to spend your time, how I spend my time.

I feel like you're usually juggling many things at once. I've just finished the Leftovers, it's a beautifully melancholic soundtrack. Do you approach film and TV commissions any differently from your other work?

They're collaborations, but I don't see them as fundamentally different from ballet or opera or anything else I do, because really they're storytelling. And music for me is a storytelling medium, fundamentally. It's narrative. And I love stories, I think we're storytelling creatures. And the collaborative aspect of it I really enjoy. Most of my work is me sitting in a room on my own going nuts. And that thing of having a story and characters and then trying to find that magic little element that will make the scene light up or tell us something different or illuminate some aspect of the story, that's really fun.

How do these commissions work? Do you get to see the shows or films and then write the music?

Mostly. Sometimes I'll write something before. Waltz With Bashir was like that.

I'm glad you brought this up, it's one of my favourite films—and a stellar soundtrack too. How did this come about?

Well, Ari [Folman] wrote me an email out of the blue saying, "I've just been holed up in a cabin on the beach listening to The Blue Notebooks on repeat, and I've written this film." I was like, "OK, crazy person." But in the end it was all true. He sent me a two-minute trailer with some of his work on it, and I thought it was really great. It was a groundbreaking bit of filmmaking. It does all sorts of new things with cinematic language. I just loved it.

Can you explain how you musically conveyed some of the themes of the film?

I wrote a lot of the music off the page, just before they'd done any drawing. That music for the "Haunted Oceans" was written off the description in the script. And there are lots of musical elements within that, technical things, which are about instability and unreliability. It's in seven, so it's asymmetrical. The way the harmony works, it's deliberately wrong. We sort of recognise it but we don't. So it's got structures which are known in it, but one of them goes backwards and one of them is upside-down. You get it but you don't get it, and in a way that's the whole image for the film—it's about him reconnecting to part of his experience which he's really not sure about.

What other collaborative projects have you enjoyed working on?

One of the people I work with a lot is Wayne McGregor. We started off with Infra, which was a ballet before it was a record. And then he directed an opera of mine, Sum. And then more recently we did another ballet, Woolf Works, which is all based on Virginia Woolf texts, which was kind of a big project.

Literary sources crop up a lot in your work, is there a reason for that?

It's storytelling again. I've always read a lot. Imaginary worlds and alternate realities, that's part of the exciting thing about being alive. I love stories; creative mental spaces and often the jumping off point for a project would be something I've read. A project like Woolf Works, which is actually three ballets in an evening on three Virginia Woolf books, is more than two hours of orchestral music. And I did think last year, "Is this wise?" Sleep is the easy one after Woolf Works. So basically I've had a bit of a year.

And you're back on the road. You recently performed Recomposed and The Blue Notebooks with the 12 ensemble. How did rewriting Vivaldi compare with what you've just done with Sleep?

That was a whole other kind of experiment. I think of it like an analogue remix because I did it on paper. All those processes we do on the computer—time stretching, transpositioning, cutting and pasting—I did all those on paper with the Vivaldi material. And wrote a bunch of new stuff, so it's kind of a hybrid creature.

Do you usually compose digitally?

I use whatever tools make sense. I started my life on paper, and that for me is the quickest way to get something down. But obviously if you're making electronic music there's no point in writing things on paper. I think the studio is an instrument. It's a really flexible, interesting instrument.

Do you consider yourself more of a studio musician than a performer?

We do play, but I don't play that much. I do about a handful of shows a year—not that many. I love playing but writing music does take time and I can't really be doing both well. I have to choose.