Although the text of Libera nos, salva nos is from the first antiphon at Matins on Trinity Sunday its plea to to the Holy Trinity for freedom, redemption, and absolution is so general in tone that Sheppard's setting which most probably dates from his time at Magdalen College, Oxford was used on other occasions not the least of them being the twice-daily readings of this very text stipulated in Magdalen's statutes. It'smore than a little unusual for Sheppard's works because as you listen you can hear the cantus firmus in the lower voice. As a result of this the rate at which the harmonies change are really rather slow and this together with its modal stability creates the mood of serenity which deepens as the piece unfolds. It's one of my favourites amongs Sheppard's pieces for this reason. Enjoy :-).