Henry-Louis de La Grange, who was so captivated by a Mahler symphony he heard at Carnegie Hall in 1945 that he devoted the rest of his life to researching the tempestuous Viennese composer’s biography, died on Jan. 27 in Lonay, Switzerland, near Lausanne. He was 92.

His death was announced by the Médiathèque Musicale Mahler in Paris, a scholarly resource center that he founded with his fellow musicologist Maurice Fleuret.

Professor de La Grange, the son of a French politician who was once held prisoner by the Nazis and an American heiress to a furniture-store fortune, inherited the title of baron on his 21st birthday but dispensed with it.

“I did not earn it,” he said in 1989. “I was simply born to it. I use the title of Professor because the Austrian government has given me that title. I feel that I have earned it.”

Professor de La Grange began earning his scholarly credentials in 1973 when, after 15 years of research, he published Volume I of his biography, simply titled “Gustav Mahler.” It became a heroic 3,600-page saga, still being revised, that distinguished him as the dean of Mahler biographers. ...