More than 25 years since his professional recording debut, Michael Feinstein has become something of a gay activist. But he remains best known as a leading interpreter and archivist of the Great American Songbook. In addition to his PBS special on the subject, Feinstein continues to tour in what he told Metro Weekly two years ago is intended as “a celebration of that great era of music,” which loosely spans the two world wars and encompasses songs from early Broadway and the Jazz Age. Sunday, April 17, at 7 p.m. Kennedy Center Concert Hall. Tickets are $40 to $75. Call 202-467-4600 or visit wpas.org.