Starland Vocal Band -- now there's a blast from the past! DC locals Bill and Taffy Danoff. Bill became a well-known DC music producer, and still performs to this day. And of course he also wrote Take Me Home, Country Roads -- John Denver's hit. Denver got a writing credit after the fact for a few tweaks made during production.
{Trivia for any DC area folks who might not know: Danoff conceived and wrote the song while driving up Clopper Road through Seneca Creek State Park in Gaithersburg, MD.)
