Oophaa was composed shortly after finishing Okho and marked Xenakis's return to the unusual chamber ensemble of harpsichord and percussion, after Komboï.

[6] It is scored for an amplified harpsichord and percussionist playing seven ceramic flower pots[2] and seven skin instruments (bongos, three tom-toms, and two bass drums), meant to be placed in a wide fan-shaped layout.

[6] Chojnacka also stated that, upon tackling the piece, she chose not to take into account the many changes of register indicated in the score, and that the harpsichordist should feel free to take inspiration from them when attempting to play the piece, as a choice should be made by the performer whether to play them or not, given the extraordinary difficulty of Xenakis's output.

[6] Oophaa has not garnered much attention since its publication, probably because it is less technically demanding than the other harpsichord pieces and the structure is much simpler and devoid of dramatic construction.

Critic James Harley described the timbral and harmonic aspects of Oophaa as "gamelan-like", remarking on Xenakis's interest in Javanese music,[1] while noting the "Harry Partch-like ringing sonority of the ceramic flowerpots first used in Komboï ".