An ancient Greek stringed instrument [see lyre]. "Lyra" as a term does not appear in Homer, and in Plato's Laws it refers to lyric poetry and music. The Homeric Hymn to Hermes narrates the mythic invention of this stringed instrument: Hermes scooped out the insides of a tortoise (χέλυς) covered it with hide, made a verticle frame from two antelope horns and strung it with sheep gut strings attached at the top to a wooden yoke. Since the "first" lyre, then, was made from a tortoise shell, the term chelys came to mean the lyre. There is some confusion about the term "lyra" in literature, since it appears in early Greek poetry (Sappho, Alcman) and fifth century tragedy as a generic word for "lyre." The word "lyra" then, is not only the tortoise-shell lyre, but can refer to any of the lyre-type instruments. The barbitos is another type of tortoise-shell lyre. Both the chelys and the barbitos are lightweight and can be played in almost any position, standing, seated, reclining, or marching. The instrument is held vertically close to (or slightly away from) the chest, assisted by a strap. The left hand manipulates the strings (see "Lyre"). The number of strings seems to vary somewhere between six and nine, with seven as the norm. Because of the shape of a totoise shell, the entire instrument has a slight curve to it. According to Maas and Snyder this instrument is often seen depicted in scenes of the Muses and Eros , and is shown in ensembles with other instruments. Women played the chelys, and it might have been used as a practice instrument to prepare (male) students for kithara and other lyre playing. It rivals the kithara in popularity during the classical period and in classical mythology, but its use appears limited to the parlor, probably because its sound quality is less powerful than the kithara. Along with the barbitos the chelys was a popular instrument at banquets and drinking parties (symposia).
Maas, Martha and Jane Snyder, Stringed Instruments of Ancient Greece, New Haven, Yale University Press, 1989
New Grove Dictionary of Musical Instruments, 3 vols., ed. Stanley Sadic, London, 1984
"Music.9. Instruments," Oxford Classical Dictionary (second ed.), Oxford, 1978