I waited for years to see my first Wagner opera. Precisely, nine years. It was Der fliegende Holländer at the Royal Opera House in 2011. I had spent the previous nine years actively avoiding Wagner – even turning off the radio when his music came on – and immersing myself in Puccini, Verdi, Rossini, Mozart, Tchaikovsky, Dvořák, Janáček, Humperdinck, Gluck, Britten and pretty much anyone else who wasn't Wagner (up to and including Birtwistle, and even post-Wagnerians like Strauss, but never the man himself). It wasn't that I didn't like Wagner – of course, because I didn't know him yet – but because I feared him. I feared the depth and complexity of his music. I feared his anti-Semitism and his Nazi connotations. Above all, I feared his audience, whom I imagined only to consist of steely-eyed experts, ready to pounce on the unbelieving, the uncomprehending, or the unhappy cough victim. So, I spent nine years discovering what I thought opera was; and then Wagner, in one evening, changed everything for me. I stumbled out of The Flying Dutchman with my heart racing and my mind in tatters. I felt like I had only just seen my first real opera.

Catacylismic change; total evolution; complete progression. Wagner did not even want his work to be called "opera", declaring opera to be dead. His "music drama" is designed on a far greater scale: an apocalyptic, semi-religious, philosophically challenging and profoundly disquieting experience, aimed squarely at your subconscious, with music which infects and haunts your brain until you can think of almost nothing else. While seeing Der Ring des Nibelungen (ROH, 2012), I was astonished to discover that in the days between the operas, I could quite literally bear to listen to nothing else. Nothing else, except Wagner. Nothing else sounded like music any more. It was an odd week. Yet the music of The Ring is, really, not music at all. It is scenery, effect, character, plot, symbol and sign. It is the whole world, universe, time, space, power, love, hate and greed. It is sound. Sound, sculptured into an edifice, which we experience as a music drama: the music drama to end all music dramas, whose end is the end of the world as we know it. And it was only one – one! – of Richard Wagner's ideas.

There are two things I love about Simon Callow's magical mystery tour Inside Wagner's Head. The first is that, like a good documentary, it coaxes the myriad elements and aspects of Wagner's life into a coherent whole. You get a brilliant linear sense of his journey, the scope of his achievement, the development of his goals, the way in which the writing of his operas fitted into the fabric of his life, and at the most simple level it just helps to understand which opera he composed when, and why, and in what order, and who he was in love with when. Some of it I knew before, some of it was new, some of the details were a delicious surprise (which I won't spoil for you – but there's a hilarious story about a dragon), and all of it was an immense help. So, getting Wagner's life in perspective is the first bonus. You feel, by the end, that you know what happened to him. In that sense it's almost like a brilliant lecture brought to life. The sheer achievement of this, in research terms, is breathtaking, as is the 105-minute uninterrupted delivery.

The second thing I love is that Callow brings Wagner's art into a rounded perspective. Callow shows us how radical – at times, terrifyingly, pyromaniacally radical – Wagner was; how his revolutionary politics were part of the process which forged his music; how his artistic ideas bled into the way he lived his life, and back again into his art (eg. Wagner as Wotan, Ludwig II of Bavaria as Siegfried). He draws our attention to the numerous autobiographical shadows across Wagner's music dramas. He discusses Wagner's anti-Semitism frankly, openly, and regretfully, exposing its hypocrisy and decrying its viciousness. Crucially, though, he shows us that anti-Semitism is not, by any stretch, the most disturbing thing about Wagner. The psychological excavation Wagner undertakes with his audience is far more profoundly unsettling, reaches even deeper, upsets us even more. Anti-Semitism was an evil aspect of Wagner the man; Wagner the artist places his burning finger on the evil aspect in all mankind, greed, and holds it there, pitilessly, without compassion or mercy. This ultimately dystopian position is the real, Schopenhauerian, mind-blinding terror. As Callow points out, there is no comfort in Wagner. The only way for the world to be saved in The Ring is for it to be destroyed, utterly. Only after opera was dead could Richard Wagner make it anew.

So, Wagner's art is on a grander scale than prejudice, even if prejudice is one of the million contradictory ingredients of his art. This does not excuse his views; they are, and will forever be, inexcusable. And, to Wagner, his position on Judaism seemed indeed inextricable from his pursuit of a German art form. But, just as we know it is possible to "hate the sin, but love the sinner", Callow’s position allows us to admire Richard Wagner's genius while acknowledging – without mercy – his gravest flaws.

Inside Wagner's Head, at ROH, LinburyCharlotte Valori reviews Inside Wagner's Head with Simon Callow at the Royal Opera House Linbury Studio Theatre.4