For Opera performances, please contact the Opera Colorado Box Office: (303) 468-2030 TTY numbers for Ticketmaster: 800-755-6244, 877-474-4833, or 877-475-4833 For Children’s Chorale performances, please contact the Colorado Children's Chorale Box Office: (303) 892-5600 For National Ballet of Denver - all ticket sales are handled by Ticketmaster.