From the time of his youth, Xenakis found solace and inspiration in the writings of the ancient Greeks, and his handful of stage works draw on these sources exclusively. One of the composer's earliest commissions came from Alexis Solomos, originally of the Greek National Theater, who had been engaged to direct a series of performances of Greek dramas in Ypsilanti, Michigan in the summer of 1966. Xenakis was hired to provide the music for Aeschylus' tragic trilogy, Oresteïa. Evidently, he provided almost two hours of music for this production; as it was not recorded nor ever again presented, little is known about the original score. Soon after the premiere, though, Xenakis produced a concert suite which was subsequently published and performed.
The suite is in three parts, following, in abbreviated fashion, the outline of the original trilogy: "Agamemnon," "The Libation Bearers," and "Eumenides." In fashioning the suite, Xenakis used only excerpts from the choruses, setting them in the original Greek and attempting to follow the rhythmic and melodic contours of the language as much as possible. The instrumental writing, while more restrained than that in Xenakis' other works, is nonetheless adventurous, incorporating various textural trademarks such as glissandi, microtones, and clusters. The choral parts, too, call for a range of sonorities, including shouting, chanting, and massed percussion sounds. This is sophisticated, at times savage, music, quite appropriate to the drama.
Xenakis' Oresteïa suite has proven to be quite popular and has even been staged on its own, the truncated text somehow retaining its coherence and dramatic trajectory. For a 1987 production at Gibellina, Sicily, not far from Aeschylus' burial place, Xenakis inserted a new section into the "Agamemnon" portion of the work. Kassandra: Oresteïa II, scored for solo baritone and percussion, incorporates dialogue between Cassandra, the prophetess who foresees the tragedies about to befall Agamemnon and his family, and the chorus of elders. The music is radically different from the choruses that surround it, highlighting the dramatic nature of the text. The range and dexterity required of the vocalist are incredible; Kassandra calls for both the extreme falsetto range and low chanting. This timbral and registral dichotomy allows the single vocalist to portray both Cassandra and the elders. In addition to his vocal duties, the baritone also improvises on a psaltery in imitation of the ancient Greek lyre. The percussionist contributes brittle punctuation to the dialogue.
For an Athens production of Oresteïa in 1992, Xenakis inserted yet another piece into the work, this time in the final section. La déesse Athéna (The Goddess Athena) again turns the spotlight on an individual character. In this portion of the text, Athena establishes a tribunal, a council of judges. After all the violence and tragedy of the drama to that point, this act marks to some extent a resolution of the drama. Xenakis brings back the baritone and percussion of Kassandra, but this time incorporates the duo into the instrumental ensemble of the surrounding passages. The vocalist again makes use of an extremely wide range, this time portraying the "godliness" of Athena, or her transcendence over human limitations.
Altogether, the final version of Xenakis' Oresteïa is an hour in length, and it remains one of the composer's major works. The addition of the solo pieces provides moments of dramatic and musical contrast, and the work has been successful both in concert and on the stage. While the different portions of the suite comprise a stylistically varied whole, Xenakis' highly original music has proven itself a worthy complement to the intense drama of Aeschylus' great work.