A cappella:

The a cappella musical Perfect Harmony, a comedy about two high school a cappella groups vying to win the National championship, made its Off Broadway debut at Theatre Row’s Acorn Theatre on 42nd Street in New York City in October, 2010 after a successful out-of-town run at the Stoneham Theatre, in Stoneham, Massachusetts. Perfect Harmony features the hit music of The Jackson 5, Pat Benatar, Billy Idol, Marvin Gaye, Scandal, Tiffany, The Romantics, The Pretenders, The Temptations, The Contours, The Commodores, Tommy James & the Shondells and The Partridge Family, and has been compared to a cross between Altar Boyz and The 25th Annual Putnam County Spelling Bee.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". In what month was Perfect Harmony's Off-Brodway debut?
October