 The posthumous collection, published by his son François in 1631, gained instant popularity.The work, steeped in Protestant moralization and chiliastic attitudes, was both anti-Catholic and anti-Spanish and was studied in Zeeland both at home and Church as part of familial religious edification.The collection contained 76 songs (including Wilhelmus, which became the Netherlands' national anthem), and unusually for the time the songs were printed in musical notation (many similar collections named well-known tunes to which a printed text should be sung).