Possible Clues:

• Part of the Mass
• Mass movement
• Lamb of God - in Latin
• Figure of a lamb emblematic of Jesus Christ
• "Lamb of God"
• Mass recitation
• Making comeback, holding note, I had chanted a part of mass
• Choral piece that is performed about beginning of day — a round
• Figure of a lamb bearing a cross or flag, as an emblem of Christ
• Part of the ordinary gains due for a change