'Octet,' soon to be a movie musical from Lin-Manuel Miranda, makes rare leap to a Chicago mainstage

In the a cappella musical “Octet,” written and composed by Dave Malloy (Tony nominee for “Natasha, Pierre & The Great Comet of 1812”), eight strangers meet at a support group for Internet addiction. Their stories mostly then unfold across songs, with some dialogue and percussive elements. The Raven Theatre Midwest premiere this spring yielded a sold out run in the company’s 130-seat theater. Now the production is getting another extension — and an upgrade, opening July 15 in the Goodman’s Owen…