found: Ensemble Corund. Library of Congress Music Division concert, 2006-03-03 [SR] 2006program notes (Gabriela Bürgler, Caroline Reitzel, Regula Grundler, sopranos; Valérie Bonnard, Carmen Würsch, Daniel Zellweger, altos; Michael Feyfar, Christophe Gindraux, John Wright, tenors; Sebastian Mattmüller, Erwin Schnider, Ulrich Acolas, basses; name derived from "corundum" "whose color, brilliance, purity, transparency, and crystalline precision are qualities emulated by this professional vocal ensemble" from Lucerne; Stephen Smith, founder and director)