This motet is surely one of the best-known of Byrd's remarkable output, yet has never been published at an appropriate pitch. The work is in 'high clefs' usually requiring a transposition of a fourth downwards, as given here. it is also available a minor third higher, i.e. a tone lower than the original print.
The piece stands at the head of Byrd's contribution to the Cantiones Sacrae, his first (jointly with Tallis) published collection, and it was the most widely copied-out of all his works, to judge by surviving manuscripts. The text is that of a Respond from the first Sunday in Lent:
Let us change for the better, for we have sinned in our ignorance, lest, surprised by the day of our death we seek time for repentance and find that there is none! Hear, O Lord, and have mercy, for we have sinned against thee. Help us, O Lord of our salvation, and for the glory of your name, free us!