Expect the unexpected at the Sebago-Long Lake Music Festival (through Aug. 9).

Now in its 39th year, the festival has some of the most provocative programing on the Maine summer music scene. Tuesday night’s concert at Deertrees Theater was no exception.

Where else could one hear Charles Dimmick, concertmaster of the Portland Symphony Orchestra, play second fiddle in a Beethoven Quartet?

Or find that quartet, Op. 74 in E-flat Major (“Harp”), sandwiched between George Crumb’s masterful “Voice of the Whale” and Rebecca Clake’s little-known and quite amazing Piano Trio (1921)?