It's actually called The Forty Part Motet (A Re-working of Spem in Alium Nunquam Habui 1573, by Thomas Tallis), and Canadian artist Janet Cardiff made it in 2001 by recording 40 amateur singers, both adults and kids, performing the 40-part composition. In the installation, one loudspeaker represents each singer. The 40 speakers stand in an oval in a soaring, 35-foot-tall gallery. Depending on where you stand, individual voices are buried in the group's great wash of sound, or the single, closest voice becomes all you can hear. It's sonic sociology. (Tacoma Art Museum, 1701 Pacific Ave, 253-272-4258. 10 am–5 pm, $7.50.)