_:nbeaababeb5da47a3bf1410c1dca11d0cxb0
<http://schema.org/description>
"Pianos lose their tuning, guitars fall out of key -- even church organs need to be tuned every now and then. For centuries, the only sure-fire way to tell if an instrument was in tune was to use a tuning fork."
<https://science.howstuffworks.com/tuning-fork3.htm>