One hundred and fifty years ago this summer, Richard Wagner wanted to change the world. Not only the musical world, but nationhood, political thought, even the idea of what it means to be human. The inaugural Bayreuth festival opened on 13 August 1876, with the first complete cycle of Der Ring des Nibelungen staged in Wagner’s custom-built Bayreuth Festspielhaus in Bavaria. The first audience included kings, emperors, aristocracy and politicians as well as Europe’s musical and creative elites (Tchaikovsky, Grieg, Bruckner and Liszt among them). Wagner, who had been a revolutionary on the streets of Dresden in the 1840s, intended the Ring’s four operas to usher in a new world, one redeemed and made wise by this epic story of power, love, redemption, betrayal and renewal.

The titanic impact of Wagner is almost impossible to grasp today. Stage design aside (having the orchestra entirely hidden in the pit and darkening the auditorium were two of his innovations at Bayreuth) his legacies are felt across the arts from the way Wagnerism gripped German philosophers and Paris’s painters and poets in the 19th century, to the seismic changes he wreaked in cultural politics, and the toxicity of the antisemitic bearers of the Wagnerian flame after his death in 1883.

But – a thought experiment – is it possible to imagine a world in which Wagner never existed? What would happen if Bayreuth disappeared with the same magical flourish that made it; what might have happened to music and culture in his absence?

For a start, Bavaria would have had more money. King Ludwig bankrupted the state to pay for Wagner’s dreams and peccadilloes. And, without Wagner, the musical vanguard would surely have been led by that complex but generous virtuoso of pianism and composition, Franz Liszt. Instead of Bayreuth, Liszt’s Weimar would have remained the centre of the 19th century’s visions of the musical future. Liszt’s ego was plenty big enough, but he never got close to the narcissism and will to power of Wagner (whose marriage to Cosima made him Liszt’s son-in-law). The court of composers Liszt inspired and admired would have flourished in Wagner’s absence, while the his own symphonic poems and his later piano pieces would have taken the place they deserve in the late 19th-century repertoire but have never quite achieved. Instead of Wagner’s gigantism and verbosity, Liszt’s pieces are musical question marks, stones tossed into the future.

Instead of a focus on late-romantic ideas of progress and development, without Wagner to urge them onwards, there might have been a greater diversity of composing voices and visions. With no Bayreuth, the Great Exhibitions of Paris and London in the second half of the 19th century would probably have been even more important in opening creative imaginations to a greater range of musical cultures. Musical scenes in Russia and the Americas, as well as France and the UK, might have been allowed to flourish without the suffocation of what Thomas Adès has called the “fungus” of Wagner’s sounds and ideas. (That’s the problem distilled to its mycelial essence: imagining a world without Wagner is like imagining The Last of Us without the mushrooms – they’re everywhere – he’s everywhere!)

The important question is what music might sound like without Wagner. His world of shadows, of continual exposition, of ideas in a constant state of forming, just as his characters are in a constant state of emotional and harmonic flux, doesn’t belong only to him. Richard Strauss or Arnold Schoenberg would surely have written the same music without Wagner, but they might have found their own worlds of connection without his influence, and languages more original, less in thrall to Wagner’s cosmology of ego and expression.

Meanwhile in the early 20th century, a world without Wagner was exactly what Debussy and Stravinsky wanted – and which they achieved, as they reacted against his influence as vividly as possible in their own music. But without Wagner they wouldn’t have had the same force to react against, so perhaps their music would have been less clearcut in its mission to escape him. Be careful what you wish for: a world without Wagner might have ended up being more – well, Wagnerian!

But that’s just the start: no Wagner, no Bayreuth, no secular German temple for Hitler to worship at. Would Hitler have set up a shrine to his favourite composer, Franz Lehár, and his confectionary operettas instead? Or would the Nazi poison have been even more venomously applied to Mozart, Beethoven and Bruckner? The impossibility of the project proves the point: a world without Wagner is almost unimaginable.

Almost. The clear historical winner in anti-Wagner world is Brahms. His vision of a past and future coalescing in the emotionally ambiguous and complex present, his personal and political convictions against the rising tide of antisemitism that he witnessed in Vienna in the 1880s and 90s: those are the clarion-calls of a radically different sensibility and creative consciousness to Wagner’s. Brahms’s music – his late piano pieces, songs, and orchestral pieces particularly – is an acknowledgment of the limits of what music can do, its power to mirror the tensions of a historic moment and to transmute them into a discourse that can’t pretend to change the world, but instead can speak from one heart to another. Brahms’s vision is anti-utopian and empathetic, the opposite of Wagner’s. Those are qualities that culture then, and the world now, needs more than ever. Imagine a world without Wagner …

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This week Tom has been listening to: pianist Simone Dinnerstein’s new album, Hourglass, ensemble works by Philip Glass with the string players of her group Baroklyn. Listen to the final movement of the Tirol Concerto to hear tempo, texture and counterpoint pushed to their maximum. It’s music that’s the opposite of predictable pattern-weaving; more like a rollercoaster that’s kept – just – on the rails. Listen on Spotify | Apple Music Classical