Here are the three Famo boxes that I sold yesterday. I'd guess the wood is old growth fir or spruce. I think the boxes are neat, and hate the thought of them being destroyed, even to make musical instruments.
After finding out what the guy was going to use them for, I remembered four pieces of wood that I had in the basement. They were given to me nearly 30 years ago by the elderly co-owner of the place where I worked at the time. They were part of the lowest shelf from an old display case that he'd gotten 20-30 years earlier. He took them out so he could store things directly on the floor, out of sight under the case and have more room. He told me the cabinet was over a century old when he got it, so that probably makes the wood over 150 years old. Like the Famo boxes, it appears to be old growth fir or spruce. At 15" square and 1/2" thick, they would be perfect for making instruments. They're pictured below, but the patina makes them look darker than the wood would be if sanded.