The London Philharmonic embarks on its 11-concert Rachmaninov: Inside Out series next week. The season-long series includes performances of all the symphonies (including the Symphonic Dances that Vladimir Jurowski conducts in the opening concert on 3 October), the piano concertos in all their respective versions (that means the originals and revisions of the 1st and 4th), concert performances of his opera The Miserly Knight, and his choral masterpiece The Bells - and much, much more. It’s a unique chance to immerse yourself in Rachmaninov’s creative world, and - I hope - to overturn once and for all the wretchedly myopic view that Rachmaninov’s only achievement was to turn sentimentality into sound. Nothing could be further from the truth, and if you need one piece to disprove it, the Symphonic Dances, his last work, is the perfect, adventurous, ghoulish, nightmarish, yet consoling place to start.

And thinking about performance practice of his orchestral music, there is a small but miraculous treasure-trove out there, in the three recordings that Rachmaninov himself conducted with the Philadelphia Orchestra in 1929 - The Isle of the Dead and the Vocalise - and his Third Symphony, from 1939. They’re all there on YouTube (although the second movement of the symphony is missing; here’s a link to the recording). If you haven’t already, you have to hear them. Just like Rachmaninov’s piano-playing, there’s a combination in these performances of complete expressive freedom and utterly compelling structural clarity and momentum. There is not a trace of indulgence in these performances: instead you experience musical ideas and emotional drama realised with maximum clarity and impact. The Isle of the Dead sears with intensity towards its main climax, whose wildness and sharp-focused power is the opposite of the lugubrious wallowing that often mars performances of this piece, and the Vocalise sings in a single breath of unforced lyricism that contemporary performances struggle to create.

But the symphony is the most impressive of all. Rachmaninov gives future interpreters of the Third Symphony a masterclass in how to build symphonic momentum even while the tempo is continually fluctuating. The result is still, I think, the most inspiring performance I’ve ever heard of this symphony. You hear so many thousands of details of phrasing and tempo and dynamics that are unmarked in the score but which are clearly central to Rachmaninov’s conception of this music. Most startlingly of all, listen to the way he stretches the second tune in the first movement, which you first hear in the cellos, creating a 4/4 bar that is so long, it seems almost to have five beats in it (there isn’t even a specific ritardando marked at this point in the score, just a general indication of “Tempo rubato”, of flexible speed, and a tenuto mark over the first quaver of the fourth beat of the bar in the cellos’ melody); but there’s nothing that directly suggests the extremity of Rachmaninov’s performance). That’s the kind of thing conductors would hardly dare to do today, but which Rachmaninov makes so obviously - and so naturally - part of the music’s structure that you’ll miss it when you hear it done differently.

On one hand, Rachmaninov’s own performance practice should empower today’s conductors to be more imaginative in their approach to his music. The problem is that our maestros now are often unable to create a real musical freedom without making it sound as if they’re turning the music into their personal emotional soapbox. But that’s one of the profound lessons of Rachmaninov’s performance of this symphony: it’s freer - and often faster - than many you’ll hear today, but it’s the one that works best structurally, too. That marking “Tempo rubato” doesn’t mean “muck about with the speed however you like”, instead, it’s a challenge to make the symphony breathe with lyrical life, but without losing its sense of line, of pulse, of narrative. Rachmaninov’s whole recording reveals a combination of disciplined freedom that’s essential to the fabric of this piece, but which we hardly hear in performances or recordings today. It will be fascinating to go on the LPO’s Rachmaninov journey with them, which climaxes with Jurowski’s performance of the Third Symphony next April. Meantime though: listen, conductors, and learn!