He began composing at the age of 13 and immediately exhibited exceptional talent in that field too. By the time he published his Opus 1, he already had dozens of works to his credit. His monumental and massive First String Quartet was composed in 1894 and was submitted for the annual competition for fine arts held by the Royal Academy of Belgium, where it was awarded the top prize by the jury.
In 1902, he returned to his native land, and in the following year he was named a professor of harmony and counterpoint at his old Liège college. With the outbreak of World War I, he and his family moved to England where he founded a piano quartet. When peace returned, he came back to Belgium and was named professor of fugue at the Royal Conservatoire in Brussels. From 1925 until 1929, he served as director of that institution; a quarter of a century after leaving the directorship, he died at Sart-lez-Spa, Belgium.
From his teens to his seventies he composed a great deal, including symphonies, concertos, chamber music (notably a late string trio and three string quartets), and songs, some with piano, others with orchestra. (His list of opus numbers eventually reached 241, but he destroyed a good many pieces.) Today, the only part of his oeuvre performed with any regularity is his output for organ, much of it solo, some of it in combination with other instruments. His Symphonie Concertante of 1926 is a tour de force, considered by many to be among the greatest works ever written for organ and orchestra.