Montreal Symphony Orchestra (OSM) is debuting a new instrument Thursday, one that will be hard to miss.

The octobass measures 3.6 metres and weighs 131 kilos.

The OSM has the distinction of being the only orchestra in the world in possession of one.

Bassist Eric Chappell is five feet 11 inches tall and can't even reach the top of the instrument.

"It's essentially a double bass but on steroids," said Chappell.

"It's about twice as tall and much wider, about the same shape as a double bass but twice as big. Its almost 12 feet tall."

Bassist Eric Chappell stands on a small stool to play the giant octobass. (Radio-Canada)

"Obviously I can't actually physically play the instrument with my left hand, I can't get that high with my arm so there's actually a series of levers on the side of the instrument that help me to play it," Chappell said.

Just how low can it go?

"We can go pretty low," Chappell said, "down to the lowest note on a piano, so, quite a bit lower than a double bass and actually lower than the tuba and the contrabassoon."

The instrument was invented in 1849 by luthier Jean-Baptiste Vuillaume in France.

The octobass Chappell will be playing is a reproduction.

"There were three originals that were made in France back around 1850, and only one of them survived intact," he said.

"It's in a museum in Paris, so this instrument was copied by a modern luthier."

The instrument will make its debut at the 50th anniversary Montreal Metro concert, Oct. 20.