Winston Sullivan, bass/baritone, sings the first aria from Cox and Box, a very funny one-act show by Burnand and Sullivan. KU Opera presents a double-bill Friday at 7:30 p.m./Sunday at 2:30 p.m. with Cox and Box plus the short Ralph Vaughan Williams opera Riders to the Sea. From Riders to the Sea, here are sisters Kathleen and Nora, sung by sopranos Jessica True and Jane Trembley. Winston Sullivan, from Knoxville, Tennessee, studies with John Stephens at KU as a third year doctoral candidate. Jessica True, soprano, is earning her Masters in Vocal Performance from KU as she studies with Joyce Castle. Jane Trembley, soprano, is a senior in Voice studying with Julia Broxholm. Mark Ferrell accompanied on piano.