Termites!

[Newton Hunt]

First, I would not let that piano in my shop or anywhere else I might
have "valuable" wood.

Second termites are the hardest little bastards to kill that live in
the in sect world.

Third, necrosis is the only effective and sure way to kill them.  Put
the piano in a plastic tent with a nitrogen tank and control valve. 
Burn iron filings in the tent to consume the oxygen and release
nitrogen to balance air pressure.  Wait a week.

Pray you have killed them all.

Likely you have not.

I would take the piano to the dump, burn it, and forget it.

I met their relatives in Cuba and I was impressed by their tenacity.

		Newton