Sia, Lauren Alaina, Darius Rucker and more stars joined Musicians On Call (MOC) and Hyundai Hope On Wheels' new series Healing Through Music that surprises hospital patients and caregivers with once-in-a-lifetime performances that launched Wednesday (May 20).MOC works to uplift bedridden patients with music, while Hyundai Hope On Wheels remains committed to finding a cure to cancer in children.