De Klerk started in 1900 at age 15 his flute, singing and composition studies at the Royal Flemish Conservatory in Antwerp. His voice teachers included Henry Fontaine and the renowned Wagner specialist Ernest Van Dijck. His counterpoint and harmony teacher was Heinrich Zöllner, but in addition he also owed the later conservatory director Jan Blockx in this respect. Theofiel Anthoni was his flute teacher. De Klerk’s interest was broader than music only: theatre was also up his alley, and in 1902 he founded a society for theatre and literature, 'De Nachtegaal' (The Nightingale) in his native village.
After his studies he became a conductor for a couple of Antwerp musical societies: the symphonic wind band St Bartholomew and the brass band of ‘the Dam’ in the North of Antwerp, a proletarian precinct. In 1910 he was officially appointed as a music teacher at several municipal schools. In the meantime he composed dozens of songs, the best-known remaining De vink (The Finch), Ik weet een huisje staan (I know a little house) and Wie kan u ooit vergeten? (Who could ever forget you?). In the spring of 1914 De Klerk was getting ready for a grand opera Baas Gansendonck (The village innkeeper), based on the novel by Hendrik Conscience. However, the war interfered, forcing De Klerk and his family into exile in the Netherlands.
He ended up in Haarlem, where he had the good luck of meeting the Dutch composer Hendrik Andriessen already on his first evening, an encounter that was to facilitate his job opportunities in Holland a great deal. Thus he was almost immediately appointed as choral conductor at the catholic St Joseph’s church (where Hendrik Andriessen was organist) as well as succeeding Philip Loots as music critic and reviewer for De oprechte Haarlemsche Courant. In that capacity he was also active as a jury member for several music competitions and examinations at conservatories, both in Holland and in Belgium. In 1918 he was co-founder of the Dutch Society for Carillon Playing. A year later he was appointed as teacher at the ‘Maatschappij der toonkunst’ (Society for Music) in Haarlem.
De Klerk completed Baas Gansendonck in 1919: the premiere took place on 1 January 1920 at the Flemish Opera in Antwerp. Furthermore he wrote several cantatas which were sometimes inspired by Flemish subjects (Vlaanderens herwording / The Regeneration of Flanders), sometimes also by Dutch subjects (Herboren Holland / Holland Reborn). In 1937 he composed a cantata for open-air performance Zo zong de Gouden Eeeuw (Thus Sang the Golden Age) for choir, orchestra and carillon, featuring arrangements of sixteenth- and seventeenth-century folk tunes. De Klerk also wrote incidental music for works by Henri Ghéon, Reinhard Johannes Sorge and his brother-in-law Anton Van de Velde. He also managed to have Benoit’s Rubens Cantata performed at the Haarlem market square. Het Vaderland reported on 23 June 1936: “On 13 July Peter Benoit’s Rubens Cantata will be performed in open air at the market square in Haarlem, an initiative of the New Haarlem Art Circle, under the baton of Jos. De Klerk. Almost all singers of the Haarlem singing societies collaborate, as well as the H[aarlemse]. O[rkest].V[ereniging]. orchestra, augmented with wind players from several symphonic wind orchestras. The carillon in the tower of the Groote Kerk will be played by Staf Nees, carilloneur of St Rombouts church in Mechelen.”
De Klerk’s significance resides - in addition to his work as a composer - mainly in his music reviews, which give an accurate image of the musical circumstances in which one had to work in those days. Besides a large number of articles he also wrote a number of books such as Uit de schatkamer der Oud-Nederlandse Polyfonie (From the Treasury of Old Netherlandic Polyphony), in which choral works are anthologized with commentaries, the book Muzikale speurtochten in Haarlems historie (Musical Investigations in Haarlem’s past) and Het Haarlems muziekleven in de loop der tijden (Musical life in Haarlem in the course of the ages), the latter being praised in 1965 by the NRC Handelsblad as follows: "This substantial book counting 360 pages impressively testifies to De Klerk’s erudition and keen nose for detection, as well as to his undiminished, youthful responsiveness to the miracle of music, no matter how that miracle reveals itself."
For his achievement De Klerk received several medals, among them the commemorative medal of the municipality of Merksem, as well as being dubbed a Knight in the Order of Orange-Nassau.
© Studiecentrum voor Vlaamse Muziek - Adeline Boeckaert (translation: Joris Duytschaever)