At hcmf// 2019, Heiner Goebbels goes rogue. Long since established as one of music theatre’s leading composers and directors, he will be represented without setting, story or script. His prop will be a piano, taking the now legendary German musician back to the days when he had to make do with an instrument and an instinct.

In fact, if you’re willing, we’ll completely disregard Composer Goebbels for a moment, and swerve instead to a time of experimental bunker rock shows, anarchic improvisation and leftist brass band action. A concert of free improvisation is, after all, a bit of a portal, a 40 year flashback to a time when Goebbels a free playing musician. Back then, he was mingling in Frankfurt’s underground scene, traversing the city’s squats and the politically charged music attached to them. It was here he spent the late 1970s as a member of Sogenanntes Linksradikales Blasorchester (the ‘So-Called Left Radical Wind Band’), seeking a reality and impact to music that remains in his music to the present day.

He was all about the bands. In 1975, Goebbels met Alfred Harth. Both musicians had been making symmetrical moves towards experimental music, bumping into one another through local jazz band Rauhreif. The group fizzled out of existence, but swung the two players closer; Harth and Goebells opted to do the show as a duo, building on some informal collaborations they had worked on in the past – echoing Rauhreif’s energy, without any of its jazz for their first concert together, Goebbels and Harth took a programme of traditional compositions and discombobulated them. They changed melodies, tinkered with structures, and as Harth noted, ‘integrated them into improvisations’. This became the format for the partnership known simply as Duo Goebbels/Harth: working on the music of composers they deeply respected, they added their own interpretations, respectfully tinkering with their inspiration.

Goebbels and Harth were a duo, but played with many other professional and amateur musicians from the Frankfurt Sponti movement, collectively forming that So-Called Radical Left Wind Band, which reached upwards of 20 players. True to their name, they were present at demos and activist functions, creating a symbiotic relationship between German music and politics, and reinventing the purpose of brass band – from state fanfare to citizen resistance. The duo later changed direction again, forming the experimental rock band Cassiber, where they would interrogate yet another format: popular music. The band counted vocalist, guitars and electronic musician Christoph Anders, as well as and drummer Chris Cutler, of the legendary avant-rock band Henry Cow, amongst its number, and released a series of records. They formed their songs around loose ideas, given strenuous improvisational workouts, often lifting classical composition into the harsh terrain of noise music.

At this point, Cassiber is a tasty slice of history in Goebbels’ career, marking the last time he’d make the kind of music you’d find listed on a website called Progarchives. As the duo developed their musical styles, Goebbels moved further along in making composed works. In the 1990s, Goebbels made a name for himself as a composer of ensemble and orchestra works and music theatre, creating large-scale stage pieces that kept intact many of his curious, inter-format ideas, all the while investigating structured world-building. Tying this work to visual, installation-based composition, he emerged with deeply stimulating works as different from one another as Landscape With Man Getting Killed by Snake and Or The Hapless Landings – works with staggeringly divergent texts, backgrounds and histories.

In writing music theatre, Goebbels became a kind of open-ended completist. He wanted to ensure that every aspect of his composition and direction – from music through to lighting, staging and artist movement – was felt by its audience, on their own terms. As he told Stephan Buchberger: ‘I attempt to present the diverse voices in the materials, which the audience can then put together to form a comprehensive impression, an experience’. Constructed out of texts from writers such as Kafka and T.S. Eliot, I went to the house but did not enter requires both acting and a cappella singing of its performers, as well as a malleable domestic setting that they must take apart themselves. These are inquisitive directions, from an inquisitive mind: rather than create a music theatre of his own opinion, Goebbels’ writes with everyone who will experience it in mind, opening them up to the same thoughts and questions he has himself. In this, there are hints of the improvising Goebbels of Frankfurt past: an open-minded lover of grey area, certain only that he’s not.

Goebbels’ theatre work is still expanding. His most recent production, Everything That Happened and Would Happen, served as a history of Europe’s permanent wartime, delivered on the century of the First World War. It weaves together an incredible suite of stage changes, making intense changes in sound, colour and environment as it surveys a continent of conflict. Once again, the piece is laid out on a vast musical map, making significant use of improvisation. Harkening back to Goebbels’ days as an amateur left-wing sax player, the piece makes use of saxophones to evoke political histories, echoing the cries of helpless, war-torn citizens. It’s an example of what Goebbels does best, using intricacy to highlight incident.

These solos were played by Gianni Gebbia, another stalwart of impression and free play. In recent years, he has been on hand to join Goebbels as an improvising partner, bringing out a rare, early-career vision of the renowned composer. At hcmf// 2019, the duo rocks up to St Paul’s Hall for one of these performances, with nothing but a deep end to dive into and one another to bounce off of. It seems like a call back, a reference to something Goebbels used to do, but he’s been here all along – seeing what’ll happen.