Kenneth Montgomery, the Ulster Orchestra's new conductor, takes a personal delight in unravelling musical mysteries , writes Michael Dervan

There has been what you might call a quiet revolution going on in Irish musical life. It's in the area of early music and period performance style. The Irish Baroque Orchestra, Ireland's highest-profile period instruments group, has transformed itself in more than name since it shed its identity as Christ Church Baroque three years ago. Under the dynamic leadership of violinist Monica Huggett it is probing enticing new vistas.

The Irish Chamber Orchestra spent three years under the direction of early music expert Nicholas McGegan, and explored that fertile new ground that has been opening up through players on modern instruments adopting and adapting the practices of the past. McGegan has been part of the movement which has seen period-performance experts graduate, as it were, to working with the world's major orchestras. Long gone is the time when Nikolaus Harnoncourt or John Eliot Gardiner worked only with specialised groups playing on specialised instruments. Harnoncourt, in particular, has been pushing out the boundaries on what can be expected in standard repertoire from the likes of the Berlin or Vienna Philharmonics, or Amsterdam's Royal Concertgebouw Orchestra.

In relation to these kind of developments, there's not actually been much movement by the RTÉ National Symphony Orchestra. The leader in the field has been its Belfast counterpart, the Ulster Orchestra. The Ulster Orchestra's last principal conductor, Thierry Fischer, began life as a flautist, and was heavily influenced by the work he did as a member of the Chamber Orchestra of Europe under Harnoncourt. His Belfast accounts of symphonies by Beethoven, Schubert, Schumann and Brahms adopted period-style practices which have never been heard from the NSO. Belfast-born Kenneth Montgomery, who takes up the reins as principal conductor next year, is set on taking matters even further.

"SOME PEOPLE," says Montgomery, "complain that the Ulster Orchestra is a small symphony orchestra [its playing strength is 63 against the NSO's nearly 90]. "I don't. Because it's probably exactly the size that a 19th-century orchestra would have been. I know, I've done the research. The Vienna Philharmonic in the 1890s was the largest orchestra in the world, with 16 first violins. The Czech Philharmonic was founded in 1890, with nine or 10 first violins. Brahms would conduct the Vienna Philharmonic, but he didn't like it. He preferred working with the Karlsruhe orchestra, which had nine first violins. We have 11 or 12. So, in fact, that's around the size that Brahms, Tchaikovsky and Dvorak wrote for, and we can cut it down for Mendelssohn, Schumann and so on.

"Mozart I would never play with more than eight first violins. And we know that Beethoven did an Eroica with four and five first violins. We know that Berlioz played his Symphonie fantastique in Frankfurt or somewhere like that with four first violins. There was a great flexibility in those days.

"We're all taught that the symphony orchestra is 14 first violins, 12 seconds, 10 violas, eight cellos, six basses," he says. "That's the formula that we as young conductors would have been taught. It's wrong. It should be equal numbers of violins, sitting on either side. There should be a proportionate number of double basses. Verdi says 10 first violins, eight double basses, and please don't put the double basses together. He wanted a particular sound out of the double basses - in other words, a surround-sound bass. That's what I do. I place the basses sometimes on two sides of the orchestra, sometimes at the back of the orchestra."

Montgomery also adopts the practice, traditional until the mid 20th century, of having first violins on his left and the seconds on the right, rather than having both on the one side. "I simply refuse to have the second violins on the left. If the orchestra wants to insist, I say I'm simply not conducting. It's wrong."

Having a smaller string section is all well and good. But developments in wind instruments over the years have actually made those instruments louder than they used to be in relation to the strings. Montgomery also has this issue in hand. He has helped the Ulster Orchestra brass players to get rotary-valved trumpets, narrow-bore trombones, and, for a Mozart series earlier this year, he had natural, valveless trumpets, and early 19th-century timpani, too. I would like to persuade our flute players to play wooden flutes. We've learned so much from the early music thing in the past 30 years, that this is what one must do. I'm perfectly convinced that a modern, well worked out symphony orchestra can be extremely flexible. They can play the really modern instruments, and they can play the older instruments equally well. It's a matter of the conductor giving them the reason why."

For him, he says, "It's not a whim. It's a passion. And I hope it's an educated passion." For Mozart, he did a lot more than introduce old-style instruments. "I had the orchestra stand. Because orchestras only began to sit down in - we know the precise year in England - in 1903. It was a little earlier in the German-speaking countries, maybe the 1890s. This of course is concert-giving orchestras, not orchestras in the opera pit. Elgar would have heard his Enigma Variations with the orchestra standing. And it makes a complete extra to the sound.

"All players practise standing, they don't sit down. There's a reason for it. It sounds better. And when a whole orchestra stands, the overtones, the brilliance, is wonderful. It's not louder. It's just richer. The reason that orchestras began to sit down is because the music became so much more complicated, with all the chromatic music it had to be organised in a different way, with a larger orchestra they couldn't see the conductor, all that kind of thing. It's logical that they began to sit down."

MONTGOMERY SOUNDS at times like a kind of musical detective who takes a personal delight in unravelling the various mysteries that confront him. He parades with pride a 1922 statement by Leopold Auer, teacher of Heifetz and many other great violinists, to the effect that the use of continuous vibrato was a matter of bad taste. In piano concertos, he reverts to the practice of placing the piano (without its lid) in the middle of the orchestra, with the soloist facing the audience. And he keeps the wind players close to the piano, because "it is terribly difficult for the winds to stay in tune with a piano".

He identifies Hans von Bülow as the man who was the first "virtuoso conductor," developing the idea of multiple rather than single rehearsals, and creating the conductor's role as we now know it sometime after 1880. Bülow, he says, effectively started the idea of "interpretation" as we understand the concept. Before that time, it was effectively a matter for the musicians. "The conductor was not then the kind of person that everyone relied on, like orchestras are trained to rely on now." In the pre-Bülow way of doing things, he says, there were effectively two leaders for concerts, the leader of the orchestra - the concert master - and the conductor. "Opera was done very much that way, the main conductor with his nose almost on the stage, conducting the singers, and the leader of the orchestra, standing up very often, and following the singers."

In the old days, of course, the demands weren't as great. The repertoire was narrower, the range of styles not so great. "Nowadays, we do thousands of different styles. So a conductor has to guide the orchestra through the different styles and also have this general technique that most people follow, so that the orchestra players know where the third beat is, or whatever."

The style for the three upcoming Mozart concerts with the Orchestra of St Cecilia will certainly be different to what the players are used to.

So, for the choral concert, of the Mass in C minor and the Requiem, he says, "I'm not sure I can manage it, but what I really want to do is the 19th-century seating of a choral concert, where the choir is seated at the front. The orchestra is behind, and the soloists also behind, beside the conductor. What I was hoping was that Blánaid [Murphy, director of the choirs involved, the Palestrina Choir and the Dublin Bach Singers]would conduct the chorus, following me. But she's rather pregnant, and I'm not sure she can do it, but I'm going to try and persuade her. That's the way it was done. The organ will be beside the chorus, with his back to the audience, and he can see me as well."

Montgomery has already asked the trumpeters of the Ulster Orchestra if they can use different trumpets for the two different works - Haydn's Nelson Mass and Tchaikovsky's Pathétique Symphony - in his concert in Belfast at the end of the month. The quiet revolution in Irish orchestral life is continuing apace.

Kenneth Montgomery's Mozart series with the Orchestra of St Cecilia is at the National Concert Hall in Dublin tonight, Mon 6, and Mon 13. His Ulster Orchestra concert is at the Waterfront Hall, Belfast, on Fri 24