The lyre is a stringed musical instrument well known for its use in classical antiquity and later. The lyre is similar in appearance to a small harp but with distinct differences. A classical lyre has a hollow body or sound-chest (also known as soundbox or resonator), which, in ancient Greek tradition, was made out of turtle shell. The recitations of the ancient Greeks were accompanied by lyre playing. The lyre of classical antiquity was ordinarily played by being strummed with a plectrum, like a guitar or a zither, rather than being plucked, like a harp. The fingers of the free hand silenced the unwanted strings in the chord. Also see cithara (kithara), and chelys.
Sources: http://en.wikipedia.org/wiki/Lyre