“Eternity” considers the intersection between the timeless and the actual, with music that seems to suspend time. It centers on the one of the 20th century’s greatest a cappella choral works, Frank Martin’s Mass for Double Choir, which is rooted in Renaissance polyphony but expressed in Martin’s unique modern voice. CpM last performed it in 2006. Max Reger’s romantic partsong “Morgengesang” celebrates the light of God in all things; and J.S. Bach’s “Lobet den Herrn” rejoices, with Psalm 117, that “the faithfulness of the Lord endures forever.”