Written for the Ysaÿe Competition, Jean Absil's first Piano Concerto, Op. 30 (1937), finally helped him to gain international notice in 1938, twenty-six years after he gave his first organ recital and 25 years after he initiated his formal conservatory studies. Despite his early interest in Richard Strauss and Wagner, he became fond of chamber music forms, writing numerous chamber works, often employing a polymodal and polyphonic language. Throughout his lifetime, he had many instructors who helped him develop his art, including Alphonse Oeyen, for harmony, organ, and piano; Paul Gilson, for composition; Desmet, for organ; Edouard Samuel, for practical harmony; Martin Lunssens, for written harmony; Paulin Marchand, for counterpoint; and Léon Du Bois for fugue. These studies took place at several institutions, including the École St Grégoire and the Brussels Conservatory. Despite the burden of his administrative duties as director of the Music Academy at Etterbek, a post he accepted in 1921, continued composing, establishing a fine reputation with such works as La Mort de Tintagiles, Op. 3 (1923 - 1926), and the Flemish Rhapsody, Op. 4 (1928). Later, in the early 1930s, he taught at the Brussels Conservatory. Absil won many awards during his studies and early career, including the Agniez Prize (1921), the Belgian Prix de Rome (1922), and the Prix Rubens (1934). The last-named prize enabled him to visit Paris. In Paris, Absil, who has taken an avoid interest in the music of Milhaud, met a number of prominent composers, including Honegger, Ibert, Milhaud, and Schmitt. During his stay in France, and shortly thereafter, he produced the bulk of his vocal compositions, setting texts by Brohée, Maeterlinck, Beerblock, Cocteau, Morgenstern, and Klingsor. Eventually he was offered a post at the Chapelle Musicale Reine in the late 1930s, where he stayed until 1959.
With several dramatic, orchestral, vocal, and choral works to his name, Absil focused his attention primarily on composing instrumental pieces during the final years of his life. He passed away at the age of eighty in his homeland, two years after completing his last composition, Piano Concerto No. 3, Op. 162. He is still remembered for having founded the Revue internationale de musique with the help of Dotremont and Leirens, and La Sirène, with André Souris, Poot, and Chevreuille. His music is still revived and recorded, primarily by Belgian musicians, such as bass-baritone José van Dam and by the Belgian Guides Royal Symphonic Band, both under the René Gailly label.