The text of Byrd’s motet (proper to Vespers) is one of twelve hymns ascribed to St Ambrose, the fourth-century French bishop who is credited with establishing and codifying a tradition of chant in the Western church, preceding the more renowned Pope Gregory in this endeavour by some 200 years. Byrd’s setting, which he designated ‘hymnus’, is in fact in a fairly contrapuntal motet style, though unusually clear and lucid in texture despite its six voices, and divided into three sections corresponding to the stanzas of the text. The third section is a triple canon, perhaps symbolic of the Holy Trinity. O Lux beata Trinitas dates from early in Byrd’s career, appearing in his first collection of church music, the Cantiones Sacrae of 1575 in which seventeen of his compositions were published together with seventeen by Tallis.

from notes by Collegium Records © 1999