Jean Sibelius's first foray into the symphonic form was the now rarely performed Kullervo Symphony. The LSO's Sir Colin Davis talks about this superb evocation of the Finnish composer's native land

Having now already delivered his cycle of Sibelius's seven numbered symphonies with the London Symphony Orchestra, Sir Colin Davis elects to complete his series by airing the far less frequently heard Kullervo Symphony of 1892. A work of gigantic and fascinating proportions, it certainly stands apart from Sibelius's other essays in symphonic form. Loosely programmatic and based on a central Finnish myth, the piece is cast in five movements and runs for well over an hour.

It was Sibelius's first foray into writing for large orchestra; and as there was no real native Finnish symphonic tradition he could turn to, the young composer looked elsewhere for models, means and methods.

Kullervo is heavily endowed with the legacies of Beethoven, Berlioz, Wagner and Bruckner. And, cast in more than four movements and employing vocal soloists and choral forces, it parallels the exactly contemporaneous Resurrection Symphony of Mahler. Although scoring something of a triumph at the time, Kullervo was largely suppressed by Sibelius during the remainder of his long life.

"It wasn't the route he subsequently elected to go down," comments Sir Colin Davis (pictured), "and so he perhaps regarded it as a false start or at least a cul-de-sac. Also, we see in the numbered symphonies that whilst Finland and its spirit imbues them all in certain ways, that presence is never openly alluded to, as in Kullervo, but merely suggested.

This is what's so fascinating about Sibelius in relation to where and when he was born. He starts off a fervent nationalist, as so many composers were at the end of the last century. But come the dawn of a new century and his 1st Symphony proper, he's already beginning to do something very different and unique."

So why programme Kullervo in the first place? "Well, for one thing, because it demonstrates the full extent of Sibelius's symphonic journey. There's Kullervo - five movements and 75 minutes; and there's the 7th Symphony, cast in just a single movement and lasting barely over 20 minutes. But leaving the drive for completeness and overview aside, I'm doing Kullervo because it's still a very valid piece in its own right. I perhaps didn't used to think so, but the more I conduct it the more I've warmed to it - fate, darkness, orchestral colour are all there but, ultimately, there's this grandiose design and life-affirming momentum, too. It's as if Sibelius is saying, Look, this is what I can do - and for a 27-year-old, he could do a great deal."

With the LSO joined by the Helsinki University Chorus, Kullervo should form a resounding climax to Sir Colin's ongoing revelatory exploration of and engagement with the sound world of Jean Sibelius.

Sir Colin Davis completes his Sibelius Cycle by conducting the LSO in the Kullervo Symphony tomorrow night in the Barbican Hall (0171-638 8891) at 7.30pm