Gilbert Kaplan: The resurrectionist

"Oh, I have one of these. Excellent sound quality," says Gilbert Kaplan observing the tape recorder. While the endorsement is nice, it's rather alarming that the conductor is communicating in musical terms before he has even sat down. Here to launch a new edition of Mahler's Second Symphony "Resurrection", Kaplan is the leading authority and one of the foremost interpreters of this vast, complex meditation on death and eternal life. It is, intriguingly, the only piece he conducts.

So how long will it take him before he starts discussing dominant-tonic melodic progressions and other knotty stuff incomprehensible to the layman? Almost immediately, as it happens. But the affable, urbane New Yorker - whose features bear an unnerving resemblance to those of the composer - has a capacity for discussing the minutiae of this fiendish score in a manner that draws you in as compulsively as a detective story. This is perhaps no coincidence, for over the past three years, in an attempt to solve the puzzles that have troubled him since he first conducted the piece 20 years ago, Kaplan has undertaken a microscopic investigation of the score which revealed more than 500 errors - from wrong or omitted notes, to notes written for one instrument but mistakenly assigned to another. From this evidence, Kaplan concluded that the Second Symphony has never been played - or heard - as Mahler intended.

"Mahler conducted this symphony many times, and was always refining it," he explains. "The changes are mostly subtle, but they were a matter of life and death to Mahler, and these details matter because in Mahler's music the details produce the Mahlerian sound." Moreover, Kaplan suggests, some of these adjustments go to the very heart of musical interpretation. "If you know that he wrote a line for a flute and changed it to an E-flat clarinet, which is a hugely different sound, you know you must make that sound come through or else what was the point of his changing it. And that's significant because it alters the whole colour of the passage.

"The study produced corrections for what was wrong, but also confirmation of what was right - instances in the score which your ear tells you cannot be true, and which others had thought were mistakes."

The process which enabled Kaplan to arrive at this new edition, now designated the official score by the International Gustav Mahler society in Vienna, involved him and his co-editor Dr Renate Stark-Voit consulting 14 autograph sources, including Mahler's original handwritten manuscript (part of Kaplan's private collection), and collating the markings and revisions which indicated the composer's last known decisions. Kaplan believes this represents the first accurate account of the work.

Upon release, the Vienna Philharmonic immediately proposed a recording: the only occasion this formidable and notoriously selective orchestra has offered its podium to an amateur.

Remarkably, Kaplan is neither musician nor musicologist. In 1967, he founded the heavyweight financial journal Institutional Investor, selling it 17 years later for a reported $100m (£60m), and staying on as editor-in-chief until 1993 because he enjoyed journalism. His quixotic musical journey began 40 years ago when the then 24-year-old American Stock Exchange economist was ambushed by the Second Symphony at New York's Carnegie Hall, with Leopold Stokowski conducting the American Symphony Orchestra of New York. "I've always loved music, and knew the mainstream repertoire fairly well, but I had not yet heard Mahler. For reasons I couldn't explain then and I can't explain now, this music sort of wrapped its arms around me in a way no music ever had before. I felt a connection."

The symphony continued to haunt him for two decades until he was struck by the unusual idea that he might unlock the mystery by conducting it. His entire musical education up until then amounted to three years of piano lessons as a child, which his mother stopped because he didn't practise.

With the same focused dedication he had applied to business, Kaplan compressed years of study into 12 months; working morning and night with a young conductor from the Juilliard School in New York, travelling around the world to hear the symphony wherever it was performed, and talking to the conductors. A chat with Sir George Solti that had been meant to last 20 minutes turned into a whole day. "When I apologised for taking up his time he said, 'You have no idea what a pleas- ure it is to meet someone from Wall Street with whom I can talk about music, because when I meet my colleagues all we talk about is money.'"

Kaplan gave what was intended to be his first and last performance of the symphony at Avery Fisher Hall in 1982 at a private concert to mark the fifteenth anniversary of his magazine. "The American Symphony Orchestra agreed to play on condition that no tickets were sold and no critics review it which I certainly supported. But a couple of critics snuck in and broke the rules." If they had expected to fuel their copy with a delicious debacle, they came away with a very different story. The orchestra, equally impressed, asked Kaplan to return.

Since then, Kaplan has been invited to conduct the piece with many of the world's leading orchestras; he opened the Salzburg Festival, a performance that in the words of Time magazine "shook the Grosses Festspielhaus to its granite foundations"; he gave the first ever performance of the symphony in China learning, as is his wont, something of the language; his widely acclaimed 1988 recording with the London Symphony Orchestra remains the best-selling Mahler recording of all time - out-performing by a wide margin even those of leading Mahlerians Bruno Walter, Bernstein and Rattle.

Kaplan's interpretation is predicated on a very precise reading of Mahler's instructions which observes every marking, footnote and nuance - elements frequently overlooked, but which Kaplan believes are indispensable in achieving the effect Mahler wanted. "There are few composers for whom there's such a wide range of interpretation, which is curious because no composer has provided more detail in the score." 'Why don't we play it the way Mahler wrote it?' is Kaplan's inevitable - and unchallengeable - response to any conflict with orchestras. "The problem with so many performances of Mahler is that often conductors have not had time to learn what's in the score. Mahler was a genius at orchestration, at expressing the ambiguity of contradictory emotions simultaneously - and you cannot get this magic without the details. I know of no other composer who tells you what not to do. Because he was a conductor, and he didn't trust other conductors, he wrote it all in. A performance is very much an interpretative matter and you must bring your own life to this music, but you have to know what's there, and that has to be accurate to begin with."

He declines invitations to conduct other work, but doesn't rule out the possibility. "I didn't do this because I wanted to be a conductor: the driving force was the music. I would need a reason to conduct something else." His only other recording, the Adagietto from Mahler's Fifth, resulted from the discovery that its funereal associations, and tempo, were entirely misplaced. "Mahler wrote it as a love letter to his wife Alma before their marriage. I'd like to believe that's contributed to a reassessment of that music, because you don't often hear it in slow motion any more."

Given the inconsistencies he has uncovered in Mahler's work, does he consider the other pieces merit similar investigation? Kaplan's eyes light up, and something of the inky-fingered journalist emerges. "Yes. In fact through the work of my foundation we're going to publish information on the Sixth Symphony which I can't discuss but which is going to be a real bombshell - something that is not only wrong, but approaches duplicity and fraud."

Away from the concert hall, Kaplan doesn't stray too far from Mahler territory, nor do his activities conform to those of the average multi-millionaire: he lectures, teaches a course at the Juilliard, presents a music programme on radio, and sits on a number of cultural boards including the South Bank. He has written a biography of Mahler, and a book on the surrealist René Magritte. A major collector of surrealist art, Kaplan makes an interesting case for the connection between Mahler's music and the confusion of surrealism - and, no great surprise, has also set Sotheby's and Christie's straight after spotting a number of serious errors in their catalogues.

He is greatly amused by the suggestion that he is, perhaps, a detective manqué. "I love the detective work because I'm intellectually curious about all this. But it has to be relevant. So many musicologists are involved in detective work which gets discussed between themselves - and then the music continues to be performed in the wrong way."

After more than 100 performances his fascination with this symphony is, he says, still nowhere near exhausted. "If I ever felt that happen, I would stop conducting. Mahler said that in every performance a work must be reborn, and almost every time I conduct I discover something in the music I didn't see before."

Mahler Symphony No 2 Gilbert Kaplan and the Vienna Philharmonic is released by Deutsche Grammophon on 4 November. Kaplan conducts the Philharmonia Orchestra at De Montfort Hall, Leicester (0116-233 3111) on 3 November and at the Royal Festival Hall, London SE1 (020-7960 4242) on 4 November