From 1946 to 1947 he studied at the Yale University School of Music and subsequently, from 1948 until 1953, privately in Paris – piano under Yvonne Lefébure and harmony, counterpoint, and analysis under Nadia Boulanger.

He carried out research in Europe and North America and over time accumulated a collection of materials which became one of the richest existing archives concerning Mahler and his epoch.

[9] The first volume of his definitive Mahler biography was published by Doubleday (New York) in 1973, and Gollancz (London) in 1974 and received the Deems Taylor Award (U.S. 1974).

The revision of the English Volume I was incomplete at the time of La Grange's death; the work was completed by his associate, Sybille Werner.

[citation needed] Lecturing on Mahler for many years, Henry-Louis de La Grange toured the United States, Canada, England, Ireland, Sweden, Norway, Belgium, the Netherlands, the Czech Republic, Hungary, Spain, Italy, Morocco and, in the Far East, Japan, Hong Kong, Indonesia, the Philippines, Australia, and New Zealand.