While there is no documentary evidence for a trip to Italy, Waelrant maintained contact with a wealthy patron there, and his madrigals the influence of some of the more progressive Italian composers of his time.
The artist married at least three times: to Maria Loochenborch (c.1547), to Anna Ablyt (or Van Covelen) (28 July 1564) and to Johanna Cleerhaghen on 3 May 1581.
[3] According to his pupil Frans Sweerts (Franciscus Sweertius), writing in Athenae belgicae (1628), he was an innovator of solmization for which he devised two new methods.
The innovations were intended to address the problems inherent to the existing Guidonian system which used three overlapping hexacords and the difficulties of mutation.
Waelrant acted as the publisher and bookseller and handled the financial and sales aspects of the operation while de Laet took care of everything to do with the printing.
Some of Waelrant's simple psalm settings in the vernacular language suggest that he was a Protestant, and there is evidence that they were confiscated by Catholic church authorities at Kortrijk.
Details of his life are sparse after 1558, but he probably remained in Antwerp, where he was active as a composer, consultant for the tuning of cathedral bells, and music editor.
Indeed, many of his motets are reminiscent of Lassus, using chromaticism, cross-relations, textural contrast, and always remaining carefully attentive to the comprehensibility of the text.
Occasionally, his use of text-painting is obvious: for example, in his chanson Musiciens qui chantez, after the word "taire" (silent) all the voices rest for a moment of silence.
He was careful to align notes and syllables, a practice by no means universal in the 16th century, and he used accidentals reliably, rarely leaving the interpretation of half- and whole-steps to the singer.