David Fennessy’s Caruso (Gold is the sweat of the sun) is a 20-minute piece for electric guitar and samplers whose UK premiere takes place at the Sonica festival in Glasgow at the end of next week. It is a hazy, feverish, wistful kind of music. At its heart is the voice of the Italian opera tenor Enrico Caruso, famous in the early 20th century for the decibels and emotional clout of his mighty top notes. Fennessy’s piece fixates on those top notes — all cut from old gramophone recordings and stretched, looped, frozen in time. A twangy electric guitar spins warped lines around this impossibly heroic Caruso choir like an unattainable fantasy: overblown and outlandish, yes, but also beautiful and strangely melancholy. “You get a piece that is always in climax,” Fennessy explains. “It’s a piece about obsession. Or maybe it is actually just obsessive.”

It’s true that pathological obsession is everywhere in the Werner Herzog diaries that inspired the Caruso piece, but Fennessy’s music itself is far from obstinate or obtuse. The Glasgow-based Irish composer is a modern romantic whose works aren’t afraid of real emotion or boldly-defined metaphors. He makes hugely poignant music around street noises eavesdropped through tenement walls or earth sounds recorded by seismometers and hydrophones. The first work of his that really caught my ear and wouldn’t let go was the 2010 Piano Trio, a score subtitled ‘Music for the pauses in a conversation between John Cage and Morton Feldman’. In it, Fennessy listens in on the erratically spacious interchange between the two great avant-garde composers — recorded as a ‘radio happening’ in the late 1960s — and fills the long gaps with delicate, intricate commentary from piano, violin and cello. The composers’ voices retain their integrity, the words retain their philosophical intent, but they also break into constituent parts of rhythm and pitches, silence and oddball organic pulse. It’s mesmerising stuff.

Fennessy grew up playing electric guitar in rock bands and only started reading music around the age of 16. He jokes that “the writing was on the wall”, compositionally speaking, when he started arriving at band rehearsals with 20-minute instrumental tracks that were “basically all bridge. You can guess how much my bandmates loved me.” Tendinitis and an increasing preoccupation with writing music shifted him away from a career as a guitarist, but he will be coming out of retirement for next week’s performances of Caruso in Glasgow. “I’m like the Barbra Streisand of contemporary music,” he jokes. “Oh lord. I know you’re going to quote that.”

Caruso was premiered in 2012 by Ensemble Klang at an electric guitar festival at the Muziekgebouw in Amsterdam. The main act that night was double-header of Jan Hammer and Andy Summers, with Caruso making for a somewhat off-piste opener. “I would say that for 98 per cent of the audience it was a most unwelcome intrusion into the evening,” Fennessy remembers. “I’ve never had to fight such a wave of people leaving an auditorium as I went to the stage to take my bow.”

But the idea behind Caruso has remained his creative muse for the past five years and counting. It started when he happened upon a strange image in a magazine: an image in sepia, somehow grotesque and certainly surreal. A man in a crisp white suit and boating hat is watching a full-sized steamer ship being hauled up a muddy, misty embankment. It’s Klaus Kinski in the 1982 Herzog film Fitzcarraldo, the tale of rubber baron who dreams of building an opera house in the Peruvian jungle and whose fictional scheme to pull a paddle steamer over a mountain became a real-life obsession for Herzog as he made the film.

“A vision had seized hold of me,” Herzog wrote in Conquest of the Useless, the diaries he kept during the filming and would much later publish. “A large steamship scaling a hill under its own steam, working its way up a steep slope in the jungle, while above this natural landscape, which shatters the weak and the strong with equal ferocity, soars the voice of Caruso, silencing all the pain and all the voices of the primeval forest and drowning out all birdsong”.

The film, Caruso, Herzog and the diaries have fuelled most of Fennessy’s major recent projects. In 2013, Ilan Volkov conducted the premiere of Prologue (subtitled ‘Silver are the tears of the moon’) at the BBC Scottish Symphony Orchestra’s Tectonics festival. That piece is a ten-minute work for orchestra whose chords are lifted from Rigoletto — it’s Italian grand opera dropped into a sonic jungle — plus a table guitar playing a massive glissando to represent the ship heading over the hill. Caruso forms the slow movement of this meta Fitzcaraldo triptych, with Fennessy describing the as-yet-unwritten third part planned as featuring “a mezzo soprano in a big frock, coming out in front of the orchestra and sing extracts of the diaries.” Think a grotesque version of Mahler’s Das Lied von der Erde, he advises, and you’re on the right track.

What was it about that image of Fitzcarraldo and the boat that caught Fennessy’s imagination quite so deeply? “Well, I like that there’s a dark humour to it,” he says. “It’s absurd. The absurd and the serious are perfectly comfortable bedfellows for me.” But he acknowledges it goes beyond that, too. “Of course the ship scaling the hill is the ultimate metaphor. I think what appealed to me is the fact that the metaphor is so strong for Herzog but that he admits he doesn’t know exactly what it’s a metaphor for. I feel the same way. This whole thing resonates with me so profoundly but I’m still not sure why.”

He suggests Sisyphus, forever pushing the stone up the mountain, or a Buddhist’s notion of obstacles being the path. “Or for Catholics maybe the ship going over the mountain becomes the Stations of the Cross, with Herzog as the Jesus-like leader of men. Maybe I’m writing an atheist’s passion. Definitely it hits on questions of belief, of why you make art. It’s all the big existentialist questions wrapped up in this very obvious and unsubtle metaphor.” Again, obvious and unsubtle aren’t words I would ever apply to Fennessy’s music, though his Herzog-inspired pieces never dodge the metaphor at their core.

Alongside the Herzog triptych he is currently preparing a new 90-minute music-theatre work for next year’s Munich Biennale. (Fennessy is one of Scotland’s finest composers but these days his music tends to be performed more in Germany than at home, and he’s particularly big in Munich — “a fact that bemuses nobody more than me,” he admits.) The music-theatre piece will feature a giant version of the Prologue’s table guitar that will constructed through the course of the performance out of thick piano wire and a resonating podium. Prototypes are currently being tested in Munich, by a man somewhat aptly called Zoro. Fingers crossed for a Scottish performance.

David Fennessy’s Caruso (Gold is the sweat of the sun) is at the Art School in Glasgow on November 7, part of Sonica festival