The Boulder-based 40 mixed-voice ensemble Ars Nova focuses on a sacred a cappella work by Sergei Rachmaninoff (1872-1943), the 15-part "Vespers (All-Night Vigil, op.37)." "Come, Let Us Worship," "Bless the Lord, O My Soul," "Gladsome Light," "Lord, Now Lettest Thou," "Rejoice, O Virgin"Šthese are all lovely, classic spiritual works, beautifully performed by the renowned Ars Nova. There are some church bells here, but mostly wonderfully harmonic a cappella!