It's one of the most unusual performances the city of St. John's has to offer — and possibly also the loudest.

The harbour symphony sees the bowl-shaped port transformed into an amphitheatre.

Seven ships provide the horn section. Everyone within earshot comprises the audience.

Delf Hohmann is conductor of the harbour symphony in St. John's. (CBC)

“We're expecting to blow the place away,” Pam Levy, one of the ship horn players, told CBC News.

Each of the seven teams is given a separate cue sheet, and each of the notes is timed to the second.

On board the coast guard vessel Louis S. St. Laurent, for example, there are two horn players — one for the high-end signal horn and one for the low-end foghorn.

It’s a dream gig for conductor Delf Hohmann. The event marks the kickoff of the biennial Sound Symposium in the Newfoundland and Labrador capital.

“We have assigned players to various vessels that are in the harbour,” Hohmann said.

“We sing through the score one time for them to get an idea how it actually works.”

After a countdown — three, two, one — the symphony starts.

Within five minutes, it’s all over.

There’s one last toot for good luck — because it’s not every day that a ship's horn becomes part of a big orchestra, with a whole harbour as its audience.