August de Boeck's main instrument was the organ like his father. He entered the Royal Conservatory of Music in Brussels in 1880, where one year later he obtained an organ prize (teacher Alphonse Mailly). His musical career was as an organist at different Belgian churches and as musical educator. In 1909 De Boeck was appointed teacher of harmony at the Royal Flemish Conservatory of Music in Antwerp, succeeding his teacher and friend Paul Gilson in the position. In 1920 he took on the same function at the Royal Conservatory of Music in Brussels. To this, he added the position of director of the Municipal Conservatory in Mechelen in 1921. De Boeck retired in 1930. He started with composing orchestral works, but vocal music takes up the bigger part in his creations. Opera, cantatas, and songs are dominant. The success of a new opera house in Antwerp producing Flemish operas (the Flemish Opera) surely encouraged composers in the area to write for the genre.
Four of de Boeck's operas were premiered there: Théroigne de Méricourt (1901), Winternachtsdroom (1902), Rijndwergen (Rhine Dwarfs, 1906), and Reinaert de Vos (1909). His late opera La Route d'Emeraude (1921) was in French and premiered at the 'Grand Théâtre' at Ghent. Although writing large works, de Boeck was at his best in short pieces, where his spontaneity and humor could shine. His Songs and piano pieces show his real talent. Musical influences can be traced back to Wagner, the Russian national school - especially Rimsky-Korsakov, and impressionism. De Boeck composed approximately 100 songs on French and Dutch texts.