Guilielmus Messaus (or Messaulx, Missau, Mechace, Messau) (1589 – 1640) is a South Netherlandish composer who was born in Antwerp. Little is known about his musical education. He started his career in the church not as a musician, but as a sexton in the church and as a schoolteacher. He married in 1614.
From 1609 up to 1610 Messaus was a sexton of St. Joris-church and in 1613 he became a schoolteacher and sexton at St. Wllibrord-church both in Antwerp. From 1614 to 1618 he was also a teacher at St Walburgis’s and St Andrews’s in Antwerp. From before 1620 he was a singer and a choir-master at St Walburgis-church, a post he held until his death. In 1620 he was temporarily suspended due to refusing to perform a plainchant-mass instead of a polyphonic one for the burial of a child.
There were more problems with Messaus due to his bad behaviour during the period 1618 up to 1621. But until his death in 1640 Messaus remained a singing master at Saint Walburgis in Antwerp. Messaus was a prolific composer and composed at least 14 masses, 57 motets, Dutch hymns, a canon and 3 secular songs in Dutch. He published two volumes with sacred music, Masses and Motets, among others Missae a 5-12 vocum, Antwerp 1633, and another volume Cantiones sacrae 8 vocum, 1635, unfortunately these two volumes are lost. A lot of his motets has been published in several anthologies. Another edition The Laudes Vespertinae is very important.
This Laudes Vespertinae B. Mariae Virginis, item Hymnus Venerabilis Sacramenti, et Hymni sive Cantiones .Natalitiae IIII. V. & VI. vocum. A praestantissimis auctoribus. M. Andrea Pevernagio, allisque compositae, cum basso continuo ad org, Pierre Phalése 1629. This Volume contains at least 17 compositions by Messaus among others 12 Christmas. It is supposed in the literature Messaus could be the editor of the 1629 edition. Messaus is now remembered mostly as a very productive music arranger of cantiones natalitiae (Christmas songs), which were very popular at that time in the Low Countries. Messaus was also an active copyist of motets and harpsichord music. Messaus wrote one Requiem mass published in 1633.