Here’s a tip from the Patrick G. and Shirley W. Ryan Opera Center’s April 4 “Rising Stars” concert, an end-of-season talent show featuring members of the Lyric Opera's elite training program: Amber Wagner. It’s great if a diva has a charismatic stage presence (like the center’s Broadway-worthy Angela Mannino), and can slip into a glamorous little black dress--but in the end, it’s the sound that counts. When Wagner’s soprano voice is raised, nothing else matters. Lucky for us, she’ll be back next year. In the meantime, as a 2007 winner of the Metropolitan Opera's national auditions, she's she can be seen in a Met documentary, The Audition, that will be shown April 19 at the same Chicago and suburban movie theaters that have been running the Met's HD broadcasts.