Radio host, author, musician, actor and Playbill.com personality Seth Rudetsky presents Not Since High School, an Aug. 24 concert at 42West that will benefit the music program at MS 245, a New York City public middle school. Guests including Sierra Boggess, Christine Ebersole, Keala Settle and Jose Llana will perform tunes that were the highlights of their school days. Here, a special mystery guest (you'll see why!) rehearses a tune from The Sound of Music. Watch Sierra Boggess rehearse a Guys and Dolls favorite.