When asked what the theme of his play was, Wilde answered ''That we should treat all trivial things in life very seriously, and all serious things in life with a sincere and studied triviality''. Gerald Barry's fifth opera based on the play is genuine comic with a dark heart. The previous four have remarkable libretti, but The Importance of Being Earnest, written in 1894, is all but perfect in its construction, and Barry's audacious approach triumphantly confounds all expectations. As Barry describes it: ''The play's bones are unshatterable. My version is an X-ray of it.'' The musical references range from Beethoven to Schoenberg, all treated with a reckless panache and impish wit, by turns dazzling, startling and charming the audience.