Between March 1544 and June 1545 he worked as succentor at the cathedral of Bruges, and shortly thereafter he began a business relationship with Tielman Susato, the publisher in Antwerp, which was to last for the rest of his life.
From 1545 until 1549 he was probably choirmaster to Philippe de Croÿ, Duke of Aerschot, one of Charles V's greatest generals, where he preceded Nicolas Gombert.
However, considering that Pope Clement VII died in 1534, before any of Clemens's music was published, and that the confusion with the poet is unlikely in that the surnames were quite distinct, it is likely that the nickname was merely created in jest rather than for practical reasons.
The 1558 text in Jacobus Vaet's Continuo lacrimas, his déploration on Clemens's death, suggests that he met a violent end, though if true, the circumstances are not given.
The Souterliedekens were published in 1556–1557 by Susato in his Musyck Boexken ("Music Books"), IV-VII[8] and comprised the only Protestant part-music in Dutch during the Renaissance.
[8] Presumably, the original verse translation of the Psalter into the Dutch language was completed by Willem van Nievelt from Wittenberg.
It is notable that these pieces of music survived the ban in 1569 when the government under the Duke of Alba censured all books that were deemed heretical.