FOR Riccardo Chailly, being principal conductor of Amsterdam's Royal Concertgebouw Orchestra is almost as good as it gets. On the one hand the Concertgebouw is one of the oldest and most prestigious orchestras in Europe, and on the other hand Chailly - at 40 - is still a young conductor, with plenty of time to contribute to the Concertgebouw legacy. Chailly has led the orchestra for the past six years. And, as he explained from his home in Milan, appointing a young conductor is entirely in keeping with the orchestra's century-old traditions. ''The Concertgebouw's chief conductors have always begun under 40,'' he said. ''That was the case with Willem Kes, that was the case with Willem Mengelberg, that was the case with Eduard van Beinum and Barnard Haitink. ''Mengelberg, for example, was 24 - and led the orchestra for 50 years.'' Chailly first conducted at the age of 14 and turned professional at 21. Among the many orchestras he has conducted are the Berliner Philharmonkier, the London Symphony Orchestra, the Wiener Philharmonika and the New York Philharmonic. And over the past 12 years, he has recorded more than 30 albums - an impressive output which garnered him four Grammy nominations. But Chailly seemed to be more impressed with Concertgebouw history: ''This year the orchestra is 105 years old - a long memory, I always say. ''There was a tradition of working with important composers, who also sometimes conducted the orchestra - like Hindemith, Stravinsky, Rachmaninov and Mahler. ''We carry these traditions on, even today, by studying and performing the old material - the golden repertoire, we call it. ''We have a marvellous archive, including the original Mahler and Stravinsky scores. ''And I remember asking when I first began in 1988 why one of the Stravinsky scores had these changes in the first violin set. ''They showed me Stravinsky had made handwritten changes, signed by him, during a rehearsal.'' But while Chailly respects the past, he is not bound by it. He is shifting - ''without forcing'', as he put it - the Concertgebouw's repertoire in his own direction. ''This orchestra is a long-term association for me, and traditionally, the orchestra has always believed and trusted in the natural sense that the conductor has inside himself,'' he said. ''Just now, my internal clock - let's call it that - is telling me that I am ready for something. ''So we are expanding the repertoire to include not only the golden repertoire but also the avant-garde and more Italian music such as Rossini, Puccini and Verdi.'' The Concertgebouw's Hong Kong performances, however, will feature works by Dvorak, Rimsky-Korsa- kov, Ketting, Stravinsky and Tchaikovsky. And from his previous experiences in Japan, Chailly expects a rapt audience. ''What we have noticed about Asia is not only a fantastic discipline but also an excellent preparation with Asian audiences,'' he said. ''You can tell that people have been studying the repertoire before coming to the concert - the way they listen, their attention during the performance. ''You can feel it. ''There is a willingness to get close to something unknown and a capacity of understanding towards the music - a commitment I would say,'' said Chailly. The Royal Concertgebouw Orchestra will perform at the Concert Hall of the Cultural Centre on September 5 and 6.