'Todd' understudy keeps his hands full

Performing a principal role in a major musical is challenging under ordinary conditions. But imagine having to master not one part but four. Then picture each role tied to a particular instrument or instruments. For Edwin Cahill, that's his daily task. The actor covers Anthony, Tobias, Beadle and Jonas Fogg in the touring production of director John Doyle's actors-as-orchestra staging of "Sweeney Todd."

"When I got this pile of FedEx boxes with music two weeks before rehearsals, I said to myself: 'Did I make a mistake? I don't think I can do this!' " says Cahill, who arrives at the Ahmanson Theatre this week with the rest of the touring company of "Sweeney." "It's the most challenging thing I've ever done. On the first day of rehearsal, I told John Doyle I was a bit daunted, and he said: 'Just remember: One, three different casts have gone through this before you, and they survived, and two, you will break down crying at some point, and that is OK.' "

Well, tears may be a bit dramatic in ordinary rehearsal conditions, but the actor-musician technique is enough to drive a performer to the insane asylum -- which may be why this "Sweeney" is set in one.

Doyle had been using actors as musicians for years before he first staged Stephen Sondheim and Hugh Wheeler's "Sweeney Todd" in Britain four years ago. "It really grew out of economic necessity," he says. "It happened in theaters that had no money, where we wanted to do musicals but couldn't afford both actors and musicians."

Doyle's first stab at the staging technique was with "Cabaret," a musical that lends itself to this treatment because of its club setting. By the time he got to "Sweeney Todd," Doyle knew that for a more traditional musical he had to figure out a presentational hook -- such as placing the characters in a mental institution, performing the tale of "Sweeney Todd." Because of this conceit, it's seemingly natural that they would be playing their own instruments. The production premiered at England's small Watermill Theatre, moved to the West End in 2004 and then to Broadway a year later before embarking on its North American tour.

"It's a complicated thing," Doyle says. "You can't have 10 understudies who play exactly the same instruments in exactly the same lineup as the people you have onstage. No producer in his right mind is going to say yes to that, so it's going to be challenging. You have to swap them around a bit but know that orally and visually every moment is covered."