An ancient Greek stringed instrument [see Lyre] The name is derived from Homeric "kitharis," meaning "string-playing" in general (see "Phorminx" for Homer's use of terms). First mentioned as a specific instrument in Theognis of Megara (640-579 BC?), the kithara is played much like other lyre-types. Its soundbox is a hollow wooden triangular or trapezoidal shape with hollow wooden arms curving gracefully upward. The cross bar, on which the tuning pegs were attached, is made of bone or ivory. If we can believe in vase paintings, the kithara had seven strings in the classical period (Eur. Ion 881 ff.), which are stretched down from the cross bar to the center of the soundbox. The instrument is pictured in mythological scenes, associated especially with Apollo, and is played by satyrs before Dionysos and Herakles. It is often depicted in an ensemble with players of the aulos. Kithara: Tuning and Performance (see "Lyre"). The instrument is held close to the chest vertically in front of the player and the strings are sounded with a plectrum, held in the right hand. The left hand dampens or stops the strings. It is most often played standing and had a loud powerful sound (Eur. Ion 882), in contrast to the phorminx, which is a smaller and probably a much softer instrument. Plato and Aristotle seem to disagree on whether the kithara is a proper instrument for use in educating the youth of ancient Greece. We do have scenes on vases depicting music lessons given on the kithara. The instrument was played during religious festivals, and soloists (κιθαρῳδόι ´κιθαρισταί) competed for recognition and prizes in music competition (αγών) during the 5th-4th centuries BC. It was also played to accompany the chorus' song and dance performances in Tragedy-- Sophocles himself was a player of some fame in his Thamyras. Plutarch (de Musica 1141C:30; 1142C:31) often mentions the two most well known kithara virtuosos Philoxenus of Kythera (c. 436-380 BC) and Timotheus of Miltetus (c. 450-360 BC). In his nomos the Persae, Timotheus claims to have invented "eleven-stroke meters and rhythms" on the kithara (Timotheus fr. 15, 229-33). The meaning is rather obscure, and some scholars believe that Timotheus added four more strings; it seems more likely, however, that Timotheus was an innovative player who embellished the melody with intricate rhythmic ornamentation. The great kithara soloists were sometimes ridiculed in comedies (e.g. Aristoph. Wasps 1275 f.).
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