Bach & Polyphonies. In an evening of firsts, the all-male Georgian choral cabal Ensemble Basiani makes its North American debut, performing with Mostly Mozart debutants Ars Nova Copenhagen and director Paul Hillier. As part of Pierre-Laurent Aimard's "Bach & Polyphonies" series, the two ensembles contrast traditional Georgian works and Bach's Jesu, meine Freude with contemporary music by Ligeti and Xenakis.