Jay Rosenblatt, 33, doesn't claim to be a detective. As a Ph.D. candidate in historical musicology at the University of Chicago, he spends a lot of his time quietly thumbing through old manuscripts in musical archives. Yet by dint of his scholarship—and a nice bit of serendipity-Rosenblatt recently turned in a piece of virtuoso sleuthing that has the classical music world agog: He unearthed a piano concerto by Franz Liszt, the great 19th-century Hungarian pianist and composer.

It seems that around 1839, Liszt, then 28 and already a public idol, wrote a number of concertos in preparation for a grand concert tour. But apparently he didn't play any of them, says Rosenblatt, who is writing his doctoral dissertation on Liszt. "I think he may have felt they were too musically adventurous." Later Liszt revised Concertos Nos. 1 (E-flat major) and 2 (A major), and both are now among the war-horses of the piano repertoire.

After his death in 1886, Liszt's papers were widely dispersed. Among the conservators was the Goethe and Schiller Archive in Weimar, East Germany, whose manuscript of the E-flat concerto has additional, seemingly unrelated music mixed in with it. The accepted view among Liszt scholars has been that these pages were early drafts the composer had meant to discard. But when Rosenblatt went to Weimar to research his dissertation last year, he made a painstaking examination and was persuaded otherwise. Though large segments of piano parts were missing, he believed the unpublished material represented a completely separate work.

Accompanied by his wife, Elizabeth, a flutist, Rosenblatt went to Budapest to continue his dissertation research. There he chanced upon a photocopy of another Liszt manuscript in the composer's own hand that had just been sent from Leningrad and was previously unknown to Western scholars. "I recognized it immediately," says Rosenblatt, spotting the piano parts that were missing in Weimar.

Together with still another manuscript page found in Nuremberg, West Germany, Rosenblatt reconstructed a "new" Liszt work. Now called the Concerto Opus Posthumous, it is scheduled for its world premiere by the Chicago Symphony next spring with Canadian pianist Janina Fialkowska as soloist. Meanwhile, Rosenblatt, who hopes to go on to college teaching, is already enjoying a measure of distinction among his colleagues. They are threatening to put a shingle outside his apartment reading JAY ROSENBLATT, FINDER OF LOST CONCERTOS.