Angelus ad Virginem describes the Annunciation, the biblical event in which the Angel Gabriel communicated with Mary about the forthcoming birth of Jesus. The tranquil music is intended to depict the angelic voice of Gabriel and the voice of Mary, through its chant-like nature and exotic, shifting harmonies.

Douglas Mason began his musical training as a chorister in Gloucester Cathedral Choir under John Sanders. He subsequently read music at Durham University, and went on to train as a music teacher at Leeds University, also singing professionally as a lay clerk in the Choir of Leeds Parish Church at this time.

As a composer, Douglas focuses on choral works in particular, and he has also written and arranged music for schools. As a performer Douglas has sung on numerous television and radio broadcasts and appeared on recordings for several labels, including Abbey, Priory and ASC records. For several years he was also a member of the William Byrd Singers directed by Stephen Wilkinson.