Zero Level
This is a standard reference audio level used when discussing relative levels. Commonly the zero levels are chosen to be 1 mW. This corresponds to 0.775 volts RMS across a 600 Ohm resistance.

A musical instrument composed of strings mounted upon a resonate frame, strings can be plucked with fingers or struck using small mallets.

My music had roots which I'd dug up from my own childhood, musical roots buried in the darkest soil.”
  Ray Charles