Here's how it works, from the email I received:
Mostly Motets will first perform each piece with the audience listening. Immediately after that, members of the audience who wish to will be welcome to sing the same piece together with the ensemble. Music selections will range from relatively familiar and easy to more unusual and challenging.Details:
Sunday, June 8, 2008 at 1:30 p.m.
First Congregational Church, 2345 Channing Way, Berkeley (Channing & Durant; Dana & Durant)
Tickets are $10 in advance, $15 at the door. Call (800) 838-3006 or visit the Mostly Motets web site to buy tickets.
The email also says this:
Auditions for the 2008-2009 season will begin the week after this performance. If you are interested, please visit the Membership part of our web site and contact Steve Moore at firstname.lastname@example.org, at (707) 575-7400, or after the concert.