One of my favorite vocal groups, the Tudor Choir, honors the 500th birthday of composer Thomas Tallis (1505-1585) by singing his brief, but nonetheless monumental, "Spem in Alium." Written for eight choirs of five singers, this a cappella motet ranks among the unlikeliest of hits for any composer.

Despite the standard-issue Biblical text of supplication before the Divine--is there any other kind?--the magic of this work rests in the individual parts sung by each of the 40 voices. A lesser composer would have concocted a bombastic mess, but Tallis deploys the voices artfully. The main vocal line passes from choir to choir, slowly piling strata upon strata of grandiose sound, which then subsides after a phrase or two. At the end of the piece, all 40 voices converge majestically, as if God had preordered a version of Ravel's Bolero but with angelic voices instead of the tick-tick-tick tidal wave of accumulating orchestral instruments.

One tip: Forget about following the Latin text. Choral composers of yore generally enjoyed the advantage of setting a well-known passage. They could expect that their educated listeners understood Latin and probably knew the text already. The uneducated were merely obliged to be tremulously worshipful. Today, we can revel in Tallis' astonishing layers of sound without the distracting gravity of meek religious belief.

The Tudors plan to sing other pieces by Tallis too, but the 10 to 12 heavenly minutes of "Spem in Alium" in the plush, reverberant space of St. Mark's should do me just fine. CHRISTOPHER DeLAURENTI

The Tudor Choir sings Sat Apr 9 (St. Mark's Cathedral, 1245 10th Ave E, 323-9415), 8 pm and Sun Apr 10 (St. Thomas Episcopal Church, 8398 NE 12th St, Medina, 323-9415), 3 pm, $15-$25.

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