Last Saturday, I spent my late night at Zankel Hall (at Carnegie Hall) passing out drink vouchers and listening in on a concert by the Alash Ensemble. They are well-known internationally for being able to sing multiple notes simultaneously!
Check out upcoming concerts at Late Nights at Zankel Hall here: http://www.carnegiehall.org/Tickets/Late-Nights-at-Zankel-Hall/
Annie at the Hall 