When composer Harrison Birtwistle put out the call for a “gloomy poet” to write the libretto for his next opera, Stephen Plaice, who prefers to think of himself as “lyrical and ironic,” found himself with the job. Over the ensuing three years, a story emerged which blends Greek myth with disturbing sexual undertones and a complex relationship which ended before the opera begins. It’s a process that few opera lovers ever think about, but a successful relationship between librettist and composer can mean the difference between success and failure.