I am slowly discovering the beautiful history of variations in the Book of Common Prayer. The 1662 and 1962 present the option of replacing the Te Deum with the Benedicite opera omnia (Song of the Three Children) following the First Lesson, and the Benedictus (Song of Zechariah) with Jubilate Deo (Psalm 100) following the Second Lesson at Morning Prayer Similarly, the Magnificat (Song of the virgin Mary) may be replaced with Cantate Domino (Psalm 98), and the Nunc dimittis (Song of Simeon) may be replaced with Deus miseratur (Psalm 67) after their respective Lessons during Evening Prayer. As an Anglican newbie, I'm wondering what governs selection between options. Are the Psalm alternatives merely to avoid repetition when the Gospel canticles appear in the lectionary? May they be used at any time? If so, why? Why is the Te Deum potentially replaced by the Benedicite? Was it to calm potential Puritan objections to using non-Biblical canticles?