Derek Jacobi as Angelo in a September performance at Sonoma State University. (Cory Weaver/Cory Weaver)

Think about my offer, hissed the villain Angelo, and get back to me after the next act of the opera. Then, the actors went to the side of the stage, and a musical ensemble began to play Purcell.

It could have been a play-within-a-play conceit gone mad. But in fact, it was an eminently enjoyable night of theater. 

As classical music looks for new forms of presentation, juxtaposing spoken Shakespeare with live music is increasingly popular. The Baltimore Symphony Orchestra’s attempt with “Romeo and Juliet” last year fell flat; this week, the National Symphony Orchestra had a few actors declaiming, extraneously but well-meaningly, between Shakespeare-inspired works. 

But on Saturday night, as the NSO was playing the last performance of its Shakespeare program in the concert hall, over in the Eisenhower Theater, the Folger Theatre and the Folger Consort, celebrating its 40th anniversary, were showing everyone how it should be done. 

One difference: The Folger was restaging a mash-up that dated from 1699, when the playwright Charles Gildon created a version of Shakespeare’s play “Measure for Measure” that included a full performance of Henry Purcell’s opera “Dido and Aeneas” during the action.

Another difference: The evening gave equal attention to the play and the opera, with excellent casting headed by Derek Jacobi in the slimy role of Angelo, who sets out to execute Claudio for presumed crimes against decency while scheming to commit just such a crime himself.

Both parts of the performance held their own, with strong playing from the consort and some colorful singing from bit players, including members of the local chorus Cathedra; Katie Baughman and Amy Broadbent almost stole the show as the maniacally laughing witches (Purcell excelled at sung sound effects) to Peter Becker’s Sorcerer, all scheming to bring Dido down. Both Becker and Emily Noël, who sang with silvery buoyancy as Belinda, jumped from sung to small spoken roles with perfect ease. And John Taylor Ward was more than competent as a firm Aeneas. If only Molly Quinn’s Dido had been slightly firmer. Her voice sounded nervous and fluttery, and she failed to supply the work’s emotional heart. Even the gorgeous aria “When I am Laid in Earth” did not quite make its effect; it sounded as if the singer were having an off night. 

The play, by contrast, came into slightly sharper focus, with Shirine Babb’s lovely Isabella standing up to Angelo, who wants to seduce her in return for pardoning her brother Claudio (Owiso Odera) — sentenced to death, ironically, for crimes against decency. Orchestrating the whole, onstage and off, was Richard Clifford, who played the Duke who ultimately sees justice served and who directed and adapted this most engaging evening.