Be careful what you say around your piano. Or around anything.

From ABC news--MIT researchers are able to recreate sounds by focusing cameras on objects that vibrate because of the sounds, such as bags of potato chips, in the same room. The video demonstration is near the bottom of the article:

http://abcnews.go.com/Technology/mit-re...d=24847498

Piano strings might be the ideal thing to film for this, given the wide frequency range? (That drone hovering outside your window isn't just watching you.)