Good ideas are everywhere in Clemency, though that doesn’t mean they’ve translated into a good listening experience in this live Boston Lyric Opera recording. Whatever success this opera had onstage with audiences is hard to discern here – not unusual with modern works whose scores are closely wedded to stage action. The opera explores the crucial Old Testament moment when aged Abraham and Sarah are visited by three severe, suspicion-inspiring angels announcing the couple’s forthcoming birth of Isaac, though Sarah is past childbearing age. We’re reminded of that birth’s vast implications – felt today in the present Middle East conflicts – with a prequel of sorts: the little-known, 15-minute ballad Hagars Klage by the teenage Franz Schubert, characterising the banishment of Abraham’s second wife Hagar and their son Ishmael.

Schubert’s inclusion would be a great idea were the ballad a viable piece of work. However, it’s best heard not as something from a promising composer but as an example of a not particularly exalted 19th-century genre. On each side of the Schubert are Abraham’s extended chants, and later, like-minded instrumental interludes in which MacMillan fuses his modern musical manner with that of Arabic music. But they occupy far more real estate than they deserve in this hour-long opera.

The dialogue exchanges between Abraham and Sarah, which are dramatically serviceable in Michael Symmons Roberts’s libretto, come off fairly leaden in MacMillan’s score, whose main musical interest comes from the imaginative treatment of the Three Travellers predicting Sarah’s forthcoming child before moving on to avenge humanity’s many wrongs. They sing as a single entity in harmonies voiced to have an effect that’s otherworldly, confrontational and full of grim purpose, later developing in myriad musical ways that are the piece’s main claim to a dynamic musical narrative.

On this recording the exposed string-writing is indicative of an under-prepared performance. The cast members are far more self-possessed though the vocal lines aren’t the sort that account for the singers’ full capabilities.