In Greek Mythology, when Hermes was a baby he stole a number of Apollo's cattle and took them to a cave in the woods near Pylos. In the cave, he found a tortoise and killed it, then removed the insides. He used one of the cow's intestines and the tortoise shell and made the first lyre.
Apollo eventually found Hermes, but fell in love with the sound the lyre made. Apollo gifted the cattle to Hermes in exchange for the lyre and forgave Hermes for stealing his cattle. The lyre then became one of Apollo's symbols of power.
The base is a hollowed out tortoise shell, two polished wooden arms sticking out one side like bulls horns. A bar connects the arms at the top and seven strings stretch from the bar to the base of the shell. It looks like a combination, banjo, harp, and dead turtle.
While in the Junkyard of the Gods, Percy finds an electric guitar shaped like Apollo's lyre.
When one of Apollo's back-up singers goes rouge, he charges Percy Jackson and Grover Underwood with the job of bringing her back. Apollo lends Grover his lyre saying it with help capture the automaton. He also warns them not to scratch it or else. When they finally spot the Celedon, Grover attempts to create a brick wall around the Celedon but fails. Next, he uses the lyre to create a bird cage trapping the Celedon inside when she transforms into a bird and dropping the lyre in the process. Percy and Grover manage to return the Celedon and the Lyre to Apollo before his concert. Apollo grows angry when he sees a scratch on his lyre, but Percy claims "it'll buff out."