The London Symphony Orchestra has been closely associated with the music of Sibelius since the early 1930s, when it recorded Symphonies Nos 1, 2, 3 and 5 with Robert Kajanus, a close colleague of the composer. In the 1950s, it recorded the first complete cycle of the symphonies under another conductor/composer (and former principal viola with the LSO), Anthony Collins. Forty years on, it has just completed a second recorded cycle (on RCA/BMG) under Sir Colin Davis, its principal conductor, with whom it is just about to launch a further cycle, live at the Barbican, starting this Sunday. Here four of the orchestra's chief players tell Mike Ashman about their big Sibelian moments.

Kurt-Hans Goedicke, principal timpanist, joined the LSO in 1964:

"What are the big moments?" he asks, handing me his part for the First Symphony. "Here you have it - and where are the rests? This is to a timpanist what a Bruckner symphony, or Wagner, is to a fiddle player. The big moment is to play this timpani part in this symphony. It starts with the first bar and ends with the last.

"You're starting straight away under the clarinet. He's playing a melody, but I am here with umpteen bars of a sustained note of B flat. Why has he put it there? You have to understand that, otherwise you'll only be playing it - and I think you ought to do a lot more! The way you put that velour carpet under the clarinet solo: it's not that you put it there, it's how you put it there.

"Sibelius makes a very slow crescendo, the peak of which is supposed to coincide with the clarinet's melodic line, then descend back into nothing, morendo [dying]. However, I start messing with it a little more than that. At the first rehearsal, I will be a good boy and do what's on paper. I listen very carefully to the clarinet and earmark everything he does: where his peak is - no two good clarinet players will play that in the same way; where there were little undulations in the melodic line; where we go away from the peak together. Next, I will go and do these undulations with him, now and then - but it should never be heard! You should just be saying `That's nice': it shouldn't be so obvious that there are little miniature crescendi and diminuendi built into it...

"In the slow movement, I take fantastic pleasure in playing some of the tiny little nuancey details in `no man's land dynamic' - you are just there, wafting in and out. Amazingly satisfying.

"The Scherzo starts with pizzicati strings and timpani solo. The timpani plays these few notes, three, four, five times. It should be easy enough - and so it is. But the way you play the first one, you have to put it in the memory bank: every time it comes again at that dynamic, you have to repeat the same. Later on, he marks it twice as loud. When you come to that bit, you feel that might be too much, in accordance with what surrounds it - all of a sudden you're supposed to be jumping out of the texture by that much - but you do! It is that dynamic that has to dictate (in hindsight) how loud or, should we say, how not loud, you might play the beginning. And that's not all! He quotes it once more to finish the movement, and the dynamic has risen to fff [very loud] - so you have to work backwards, put the roof on first to see where the foundations fit."

Ian Bousfield became principal trombonist in 1988, at the age of 24:

"The Seventh Symphony has a trombone solo which comes three times. The first time is one of the reasons why I play first trombone in the LSO."

Bousfield was on a solo recital tour in Japan a couple of years back. "People in cars to pick you up, take your suitcases, solos all night. I thought, This is great! Maybe I'll do this for a living." Back at the LSO, his first gig was Sibelius No 7. "That solo is like the culmination of Sibelius's symphonic output, the resolution of so many things. I played that and it just wiped out everything I'd done in the two weeks before. I realised that, as a trombonist, there was only one place to be - and that's in an orchestra.

"The parts are fantastic. Like Schubert in some ways, they sit on the instrument so well. Sibelius has a way of scoring where it's very difficult to sound bad playing it. The Second and the Fifth Symphonies get quite heavy towards the end, a little tiring. Otherwise, it's relax, sit back and enjoy.

"But what I'm looking forward to most is the opening of the Sixth Symphony. It's not often a hardened professional musician will actually get the CD out and listen to it over and over again. Wherever Sibelius is emotionally, Colin [Davis] manages to take you there instantly."

Liz Greaves is a rank and file first violinist, a member of the LSO Board and a frequent soloist / leader with other orchestras:

"Sibelius is very enjoyable, never unplayable (unlike bits of the Mahler Seven we've just been doing, which seems unnecessarily complicated) and feels like a well-oiled machine. Fast, delicate passages can be very tricky - there's so much important atmospheric staccato string playing. The very long build-ups to climaxes are also difficult: you have to gauge the dynamic properly, otherwise it's tempting to go flat out with climaxes all over the place - because they're such wonderful tunes. You have to hold it back a bit. Thinking about Finland and the snow helps to try and make a slightly colder sound, rather than a German sound - not too much vibrato all the time.

"The Fifth is my favourite. At one point in it, Sibelius has the whole string section in canon with all the wind and brass. You just give everything - it's a very enjoyable physical sensation with the violin to just let rip on the strings."

Roy Carter, principal oboist since 1988:

"You've got to remember that Sibelius was notoriously well endowed, an absolute drunkard, and a hooligan. Did you know that? He never directed his own music other than loudly - he didn't like the `softly, softly' approach. At times of trouble, he always resorts to huge string tunes - and we're the sort of filling: we are lighter and have to be very flexible. It's quite difficult to achieve. It's just got to sing!

"I don't think any oboist would ever tell you that Sibelius was comfortable. Look at the solos you have. In the First, the Scherzo [he sings a few notes] - very nasty, and they go lower and lower and lower. If you pull anything other than a very flexible reed, you're in trouble. Same in Two [he sings from the opening of the first movement] - it's got to be terribly light and sound terribly easy. It's atmospheric, rain drops - something like that - it's got to have that texture. The Fifth's difficult - the opening, again a very tricky key. You find the solo parts are not where you like them - they're not in the meat of the instrument. A lot of them are round in the middle, always with Cs and D flats, side E flats - he puts you right round the tricky alternative fingering part of the instrument.

"No 3 is very lyrical, with beautiful tunes for the woodwind. That one does lie well. He wrote it differently, very much as a woodwind piece. But in most of the others we're flitting around - a few odd solos here and there. But he knew what he was going to get, writing the way he did, and when he put his mind to wind writing as such, it's beautiful."

LSO Sibelius Cycle: 16-30 Nov, Barbican Hall, London EC2 (0171-638 8891)