19: The number of Red Rocks Amphitheatre concertgoers at each sold-out show who may be bone marrow matches for cancer patients in need of donations. Love Hope Strength Foundation, a Denver nonprofit, sets up booths at Red Rocks shows where healthy adult attendees can become internationally registered bone marrow donors after a simple cheek swab. If you end up as a genetic match (one in about 500 people), rest assured that most donations are made through an extended blood-draw process, which retrieves the necessary stem cells. Since its inception in 2007, Love Hope Strength has matched about 2,300 pairs. So now you’ve got something to do once you’ve claimed your seat and are waiting for the opening act to start.