Can a piano be referred to as furniture?

In the sentence:

The main space contained several pieces of furniture, such as some tables, several cabinets, and a grand piano.

is it ok to refer to include a grand piano in the enumeration of furniture? I am not sure what the boundaries of furniture are, and whether pianist may take offence at this.

I think you want furnishings. Merriam-Webster gives

: an object that tends to increase comfort or utility; especially : an article of furniture for the interior of a building —usually used in plural

For example,

The main space contained several furnishings, such as some tables, several cabinets, and a grand piano.

or

The main space was furnished with tables, several cabinets, and a grand piano.

A piano is a well-known instrument, but given its size, form and the quality of its manufacture, it is generally considered also a "valuable" piece of furniture:

From chicagotribune.com:

• A piano isn't simply a musical instrument. It's fine furniture, often the most expensive piece in a home. It becomes the focal point of whatever room it's in," says interior designer Elizabeth Pascoe, owner of Paris Flee Market in Mission, Kan. "The seating arrangement works around it."

I disagree with the currently accepted answer : furnishings includes pieces too small to be furniture, such as curtains, possibly wall hangings or paintings and so on.

A piano is a musical instrument and a pianist may be insulted to see it considered merely "furniture". However in some times and societies, it has also been a normal and expected part of the furniture in a civilized household, whether or not anyone plays it regularly - or slightly pretentious if nobody does. Or more than slightly pretentious if it's a grand piano.

So, listing a piano as furniture may be a sly way of telling us something about the household, and not necessarily complimentary unless one of the characters actually has some musical talent.

The "Chicago Tribune" quote in another answer turns this notion on its head, suggesting that its role as furniture is even more important than its music - and perhaps for their audience, that might be so.