Pioneer Valley Cappella celebrates its 40th season with “The Unending Stream,” music of Johann Sebastian Bach and his esteemed relatives, artfully curated and directed by Geoffrey Hudson. The Bach family dominated the musical world of eastern Germany for six generations and this selection of music beautifully illustrates why that was. The concert also features work by Peter Schickele, otherwise known as P.D.Q. Bach, “the twenty-first of Bach's twenty children.” With musical guests Grant Moss, keyboard; and Wayne Smith, cello.

Performances are Friday, May 4, 7:30 PM, at Grace Church, 14 Boltwood Ave, Amherst; and Saturday, May 5, 7:30 PM, at Edwards Church, 297 Main St, Northampton. Free will donations will be accepted at the door.