Gavin Bryars' music presents the listener with sublime paradoxes. It sounds both familiar and uncanny; archaic and modern; elegiac and impassive. His unfurling melodies tug at the heartstrings, but drift away from any anticipated climaxes. His scores draw on 20th century minimalist and experimental music, refracted through Renaissance choral music, cushioned by an Edwardian gauze of dark-hued strings. It's music for time travellers.

Bryars turned 80 in January, and this year ends with a multitude of opportunities to hear his work live around the UK, including several involving the composer himself. His music generates a particular kind of atmosphere, which has recurred across all six decades of his career. There's a meandering, "underwater" quality, and something nostalgic about it. This dates back to his first major work, 'The Sinking Of The Titanic' (composed between 1969 and 1972). In that piece, the episcopal hymn tune 'Autumn' (believed to have been played by the ship's band while it sank) is gradually submerged under grainy tapes of documentary material, voices and field recordings. The work is clearly influenced by the indeterminate music of John Cage (particularly his multi-layered "musicircuses"), but has an emotional immediacy, like a faded family photograph.

"I like the quality of sentimentality in various things," says Bryars. "When I used to play at a working men's club in South Yorkshire, a lot of the musicians and the comedians built everything on sentimentality. But it's something people find hard to handle. There is a kind of beauty and a strangeness about sentimentality, which is hard to pin down."

Besides his youthful stint working in the clubs, Bryars earliest musical activities were as a bass player, especially in the trio Joseph Holbrooke, alongside guitarist Derek Bailey and percussionist Tony Oxley (their music was free improvisation, but they borrowed their name from a late-Romantic English composer with an Edgar Allan Poe fixation). Under John Cage's guidance, Bryars' 1960s and early 70s text scores became key works of the English Experimental movement. This was a loose association of composers (among them Cornelius Cardew, John White, and Howard Skempton), whose music shares a wry, somewhat pastoral sensibility, far removed from the propulsive and quasi-scientific scores of US minimalists and experimentalists.

Bryars' work from this period has a streak of dadaism running through it. For example, 'Far Away And Dimly Pealing' (1972) is predicated on the instruction to "cause sounds to occur at least one mile from the performer". In 1970, Bryars was also a founding member of the Portsmouth Sinfonia, an art-school ensemble whose rejection of the notion of musical ability led to notorious, hilarious performances of standard orchestral repertoire, piquing the interest of Brian Eno, who joined on clarinet. Bryar's mischievousness and intellectualism led to a parallel interest in experimental literature, in the works of the Oulipo group of writers, Raymond Roussel and the "science of imaginary solutions", 'pataphysics.

These esoteric influences might not suggest a career trajectory into mass appeal, but Bryars' work has found an international audience in the last 50 years. In part, this is due to the success of 'Jesus' Blood Never Failed Me Yet' (originally written in 1971 and recorded and reimagined many times since). In this work, the singing of an anonymous homeless man (unlocatable and presumed to have died before the work's completion) is heard on a tape loop. This fragile, disembodied voice is gradually illuminated by instrumental chords: an orchestral halo. The effect is both profound and openly sentimental.

Bryars has been prolific since the late 1970s. On a surface level, his music appears to settle into more conventional forms throughout the 80s and 90s: concertos, five operas, four string quartets, and a multitude of choral pieces setting a range of poetry and sacred texts. But even his major commissions feature some disorienting mechanisms, such as his second opera, 'Doctor Ox's Experiment' (1998, based on the Jules Verne story), which moves in musical and theatrical slow motion, and features a jazz bassist in the orchestra, or his piece in collaboration with artist Juan Muñoz, 'A Man in a Room, Gambling' (1992), designed to be broadcast without introduction or context, late at night. These are tender paradoxes: haunting ideas, deployed with equal measures of irony and melancholy.

'1-2, 1-2-3-4' (1971)

GB: I worked as house bass player in a working men's club for a year and a half. This piece is like after hours in the club: the cleaner's just sweeping up and moving the tables away. One of the things that I started to develop when I was making this sort of experimental music was the idea of a piece where nobody has full control. I called this "private music". The audience will hear something; the performer hears something else. Then there's something which nobody hears: the totality. In the case of '1, 2, 1-2-3-4', each player is listening individually to a cassette recording on headphones. For my own versions, I use music by Johnnie Ray [the 1966 compilation Mr. Cry]. He was a very sentimental pop singer and the thing about this album is that every track is exactly the same tempo. It drifts along at this steady, steady beat and each person is playing along. As a bass player, I can hear the song, and I'm playing the bass part and everyone else with their instruments can hear their part on the on the headphones. But because it's on cassette, they sort of drift apart. It's a kind of strange deconstruction of the song. It doesn't sound quite right. It's an almost philosophical game I was playing with through the act of composition at that time.

'Jesus' Blood Never Failed Me Yet' (Obscure Records) (1975)

GB: I had no ambitions for the piece at all. We initially made a little recording with just the instruments we had. And eventually I did this version for Brian Eno, on Obscure Records. The name of the label, "Obscure", was deliberate for both Brian and myself. I wanted to recreate a specific kind of pleasure: when you're looking for something and find a single reference in the index of a book you hadn't expected. Which is the opposite of proper record company marketing, but then it developed a kind of cult following. When I made the second version in 1993 for Point Records [Philip Glass's label] and it was nominated for the second Mercury Music Prize, that's when it became more public. Paul Gambaccini told me that when he played it on Classic FM, he had more responses to it than to any album he had ever played, both "for" and "against". There was a lot of press, including a campaign against it by The Daily Star, who said I was exploiting the homeless. But I don't feel that it's exploitive of the old man's situation. It's raising him to a status that he should have: [one of] dignity and respect. There's a nobility I find in him. I became aware of the power of that man's voice when I first started working on it. I decided whatever I added to it was not going to point to me, but to enhance his qualities. It's been over 50 years of playing it. When I'm standing on the stage, whether it's with my ensemble or an orchestra or whoever, and that first entry of the voice starts, I still feel something. It still hits me. Then, when we start to play and the chords come in little by little, I'm still touched.

Gavin Bryars and Juan Muñoz – 'Programme 10 (Reprise: Dealing From The Bottom)' from A Man In A Room, Gambling 1992)

GB: I met Juan Muñoz through ArtAngel, who specialise in putting artists into non-gallery contexts. He had this idea about creating something for radio broadcast, and I was very curious what a radio piece would mean to him as a sculptor. I mean, would it be the sound of someone just hitting a chisel or something like that? We came up with these ideas about card magic, card tricks and so on, which came from Juan's interest in a particular card specialist, S.W. Erdnase, a very mysterious man. We made ten identically structured pieces, each exactly five minutes long, so it could go on rather like the shipping forecast, just before the news. The idea was that it's the kind of thing that people would encounter in passing. It was a wonderful experience to work with Juan and we became huge friends. And when he died, I was devastated. I love the sound of Juan's voice. For me, Juan is the essence of this piece.

Gavin Bryars Ensemble – 'Epilogue From Wonderlawn' (1994)

GB: It's a kind of lullaby: very, very simple. When Aphex Twin did a version of 'The Sinking Of The Titanic' for me ['Raising The Titanic', 1995], apparently at the end of each gig he would play 'Epilogue From Wonderlawn' to wind down, to bring people down to a "peace and quiet" level. Originally it was just for the four players in my ensemble. Now all four of my kids play it with me from time to time. I have such great players: my viola soloist, Morgan [Goff] has such a beautiful sound. So, this piece is just a long, extended melody. It's a different craft to do something like that, like a six-minute aria, without being operatic or having words, and it has shape and moments of repose. And I would say it's never dull. Although I'm not the one to judge that, of course.

Gavin Bryars, Hilliard Ensemble, Fretwork – 'Caedmon's "Creation Hymn"' from Cadman Requiem (1998)

GB: I was working in experimental music during the 70s and early 80s. Then I wrote my first opera [Medea, in collaboration with director Robert Wilson, originally staged 1984]. If you do that, suddenly you're thrown into a public arena. My name was known a little bit more and I had commissions from two quite serious, high-level quartets: the Arditti Quartet, for my first string quartet, and the Hilliard Ensemble, who I became very close friends with. By working with them, I got to understand all kinds of "early music" values. I started listening to Palestrina, Monteverdi, Gesualdo, and even earlier 12th century Medieval song. I now feel like a Renaissance Italian composer. I find little pleasure in the sort of dramatic, overblown, operatic world where people are just belting it out with heavy vibrato. The Cadman Requiem came about because my sound engineer, Bill Cadman, was killed in the Lockerbie air crash. I was very badly affected by that. One of the things that helped me was to write some music for him: a requiem. But it seemed to me that almost all the Latin requiem texts were inappropriate; they were asking for forgiveness. Bill needed forgiveness for nothing. Of course, Cadman's name is a sort of corruption of Caedmon, the first English poet we have, from the seventh century in Whitby Abbey, and I know Whitby very well, because it was where I went on holiday as a child. These things, together with the combination of the early music voices, made it something quite personal. I find it awkward to be that direct, but I needed to do it. It was almost a kind of therapy.

Gavin Bryars / Toivo Tulev, Estonian National Male Choir – Silva Caledonia (2008)

GB: I find Edwin Morgan's work absolutely incredible. He was a virtuoso poet: very prolific, writing a lot of experimental poetry too. He wrote these forty sonnets for Scotland, relating to aspects of Scottish landscape and life, and this was the first one I set; I think I've now set about twelve of them. This is the first thing I did for the Estonian National Male Choir. It is the largest professional men's choir in the world, and they have an unbelievable power when you hear them live. They have this big, slightly raw sound — well not raw, since it's really quite refined — but there's an energy and passion. It's really hand on heart and full blooded. In my first opera — the first time I worked with orchestras — I took the violins out. It was violas downwards. My own ensemble doesn't have violins. It's the low strings and the low-pitched [instruments] that I generally go for. In that way, these guys are perfect. You have four of the basses who can go way, way down, below any kind of known territory.

Jess Walker, Gavin Bryars, Joe Townsend, Jim Holmes – 'The Briar And The Rose' from Mercy And Grand: The Music Of Tom Waits And Kathleen Brennan (2012)

GB: Tom Waits got in touch with me around 1987. He wanted to ask if it was possible to get a copy of the original vinyl of 'Jesus Blood', because he'd lost his, and it had been deleted. He said it was his favourite album, which to me is very high praise. So, we started corresponding. When I did the second [75 minute long] version of 'Jesus Blood', I remember talking to the chief executive of the record label about strategies for a more complex orchestration, and I just said, "At 55 minutes, Tom Waits comes in!" He was astonished. I hadn't spoken to Tom about it at that point. Everything played in that piece is usually accompanying the old man. But in this case, I wanted to add someone who performs with him, as if he had a companion. When Tom joins in it's like they're on the journey together. The day I spent working with him in the studio on California was one of the most enjoyable days I've had. Years later, Opera North had this idea of producing a project called Mercy And Grand, looking at the music of Tom and Kathleen Brennan, as his co-writer. The idea was you would hear the quality of the music and text without being distracted by his idiosyncratic performance quality. I love Tom's work. I mean, he's a complex guy. He has a very big range of interests and abilities.

Gavin Bryars and Blake Morrison – 'The Stopping Train (Part 4: Ferriby To Hessle)' (2016)

Gavin Bryars: Goole is my home territory. I'm actually one of the very few season ticket supporters of Goole Town (as well as Nottingham Forest) and the river at Goole has always been important to me. I was approached by an organisation called SoundUK, about me writing something to do with a train journey. I decided to create a kind of soundtrack for travelling on the route from Goole to Hull, which I had a close relationship with, through friends of mine at school arriving from stations along that line. I timed the soundtrack precisely to the times between the various stopping points. In his words to this piece, Blake [Morrison] initially muses on aspects of the North and that area of East Yorkshire: he talks about me and the place, then he's slightly more philosophical, and then talks about historical things. You have that whole thing on the pronunciation of the word "brough", which is very funny, and then the poignancy of the Humber bridge and suicides. So, it becomes quite a melancholy piece at times.

Father John Misty – Pure Comedy (2017)

GB: Iarla Ó Lionáird — the Irish singer who I've worked with a lot — rang and said Father John Misty [Joshua Tillman] was interested in me arranging some music for an album he'd written. We recorded in the studio in Hollywood, in the Summer while I was on the West Coast [Bryars spends part of each year in Victoria, Canada]. Unusually, he didn't want to hear any samples beforehand: no mp3s, no mock-up of the arrangement. I was staying at the Chateau Marmont on Sunset Boulevard and was given drivers with black Mercedes and shades, everywhere I went. When I was conducting the band, if I was thirsty, within seconds there'd be a margarita in my hand. It was like a rock & roll paradise! What I like about Josh's work is that it has something of singer-songwriters like Randy Newman, or Tom Waits even. The kind of writing that you might finder earlier in cabaret. A narrative that's not conventionally pop music.

The Crossing – A Native Hill (2021)

GB: This piece was a gift to [Philadelphia-based choir] The Crossing. Whilst writing it, one of my daughters was on a skiing holiday with her partner and four months pregnant, and we got a message in the middle of the night that she had found him dead on the bathroom floor. Suddenly this took on an intensity that it hadn't had before. As it happened, I finished the piece on the day her child was born, so it became even more personal. Wendell Berry is remarkable writer and also has this remarkable indifference to success and fame. I chose the texts for A Native Hill from quite an old collection of his writings from the 60s, but it was hard to locate him, because he doesn't use email or give out any details about himself. I eventually found him through this guy in California, Jack, who runs a small poetry prize in Berkeley. He said Wendell Berry doesn't give permission for anyone to use his texts, but also doesn't not give permission [because] he's agnostic! When the piece was finished, I sent a two CDs, one for each of them, but Jack said he doesn't think Berry has a CD player. He might have one in his tractor, but it might be broken. I don't know whether he has ever heard it.

The Gavin Bryars Ensemble perform on 11 October at the Attenborough Centre for the Creative Arts in Brighton, with a programme including 'Jesus' Blood Never Failed Me Yet'. Other birthday concerts with the Ensemble and Phaedra Ensemble have been organised for this Autumn and Winter