One of the great pleasures of a good repertory company -- and Trinity Rep ranks high among this sadly dwindling breed -- is the opportunity it offers to observe a wide range of familiar actors trying on new roles. It's a hall-of-mirrors effect, in which the actors' current embodiments refract their cumulative resumes. With Rupert Holmes's ingenious 1985 musical ''The Mystery of Edwin Drood" -- an extrapolation of Dickens's last, unfinished novel -- the delights are further multiplied. We get to see the talented Trinity ensemble, the ragtag Victorian music hall performers that they're playing, and the penny-dreadful characters that the latter portray. Under acting artistic director Amanda Dehnert's deft direction, it's a sprawling, lively work, sometimes a bit diffuse but always engaging.
It falls to the hammy Chairman (MC) of the seedy, provincial Music Hall Royale (Brian McEleney) to explicate the action and keep it moving, all while riding herd over the music-hall actors' overweening egos. As celebrated male impersonator Miss Alice Nutting, Rachael Warren lends a jaunty, devil-may-care attitude (''Aren't I half a toff?") to the play-within-a-play's brash young hero, Edwin Drood, who may or may not be murdered midway through; she's also a hoot when Nutting turns huffy diva. Playing Rosa Bud, Drood's fiancee, Jessie Austrian -- still a student at the Brown/Trinity Rep Consortium -- is a true discovery. Unleashing a pure, strong voice (her ''Moonfall" haunts), she effectively straddles the pale Victorian victimhood of Rosa and the hoydenish brashness of the actress's offstage persona.
As choirmaster John Jasper, an unrepentant lech who leads a double life, Michael Hance is suitably creepy and a real powerhouse of a singer. And company veteran Anne Scurria tackles the bawdy role of Princess Puffer -- a fallen woman turned opium entrepreneur -- with gusto. Her Cockney-inflected anthems, ''The Wages of Sin" and ''The Garden Path to Hell," bookend the show brilliantly.
All the actors frequently fan into the audience to initiate interaction (set designer Eugene Lee has reconfigured the hangar-like Chace Theater to render it more intimate), and Puffer's visitations are especially uproarious. My only cavil with the new setup is that if you're seated too near the in-house orchestra, a lot of the lyrics are obscured, and occasional over-amping only adds to the problem. The effect is especially egregious in the opening number, ''There You Are," which introduces the Music Hall company.
In being allowed to determine the show's outcome by voting for the murderer (the denouement thus varies nightly), audience members are implicitly encouraged to play favorites. There are truly no small roles -- not when a nobody like Bazzard (Stephen Berenson) can steal the show with a bit player's lament, ''Never the Luck (and Never the Lead)." Equally winning is Stephen Thorne as a dim-witted, gap-toothed assistant gravedigger, who proves a sly charmer when it comes time to conduct the audience poll. And as mysterious Ceylonese twin orphan-refugees (what was Dickens thinking?), Mauro Hantman and especially Phyllis Kay maintain the caricature-like archness that this type of endeavor requires -- and rewards.