As the actors move across the stage, the music swells triumphantly; falls away eerily; pauses dramatically.

When Malcolm Dow is doing his job well, you won't even notice he's doing it at all.

Dow is the sound designer and composer for this year's production of Shakespeare's Pericles at Vancouver's annual Bard on the Beach Shakespeare festival — a role often overlooked by the theatre-going public, but one Dow says is even more important than in film.

"People think, oh, you don't need a sound designer for a theatre show, it's just going to be a toilet flushing and a doorbell — you know, a couple transition clips," he said.

"I think it can really provide a rich environment that brings the show to life, because theatre is so much about making the audience really buy into the story.

"But there's some people that won't even notice that [the score] is there," he continued. "I think in some ways that's what you want to do, is to make it seamless in the show."

A particularly challenging production

Pericles presented an interesting challenge for Dow because, by his own admission, it's not a very good play.

"I mean, it's a riveting story, it's an amazing story, and an incredible hero's journey," he said. "You can almost think Game of Thrones set in ancient Syria."

"But the writing is not as good as some of Shakespeare's other plays, and he's only partially responsible for it."

So, Dow had his work cut out for him if he wanted to the audience to really buy in — compounded by the fact that he had no prior background or training in the music of the Middle East.

That, combined with the grueling rehearsal schedule, meant Dow was working on music for the play well into technical rehearsals. But he finds that's actually an integral part of his theatre-scoring process.

"For me, the [rehearsal] process really reveals so many things that the script doesn't," he said. "There's moments that you just might not have foreseen."

In fact, Dow often finds himself writing well into the preview stage, when there are actual audiences watching the production.

"I've had times where you come up with a show-stopping or a show-winning sound piece that you only come in with on the last day," he said.

"I'm still listening, because there might be one really important ingredient that's not there yet."

Pericles runs at Bard on the Beach until Sept. 21.

With files from CBC Radio One's North by Northwest.