"simultaneous performance" is correct and can be used in written English.
You can use it to refer to two or more people or entities performing the same task at the same time. For example, "The simultaneous performance of the orchestra and choir created an awe-inspiring sound."
In this paper, we propose two architecture-based analytical methods for simultaneous performance and reliability (performability) evaluation of real-time component-based software: one is accurate and the other is approximate.
Choral singing may also entail the simultaneous performance of separate musical lines (polyphony).
Combining several lines of melody at once is polyphony; varying a melody in different ways in simultaneous performance is heterophony; combining melody and chords is homophony.
Another simultaneous performance of Chopin's music, this one geographic, will take place on Sept. 4 when classical, jazz and rock musicians present "4cities4Chopin" in Warsaw, Paris, London and Shanghai.
Another person who saw the light is Ara Guzelimian, a composer, pianist and music historian, who was walking through the California Institute for the Arts in 1976 when he came on a simultaneous performance of two pieces by Cage: "Winter Music" (for 20 pianos) and "Solo for Voice," sung by Ms. La Barbara on a staircase in the two-story main hall.
For instance, the canon Ma fin est mon commencement (My End Is My Beginning), by Guillaume de Machaut, the leading French composer of the 14th century, demands the simultaneous performance of a melody and its retrograde version (the notes are sung in reverse order).
The opening night, on Monday at 8, will feature three simultaneous performances in the three spaces.
At other moments you are beholding three simultaneous performances of the same drama.
"War of the Worlds" was less logistically elaborate, but it did involve simultaneous performances in various locations.
Maintaining the illusion of two simultaneous performances requires intense coordination, not to mention concentration, from Mr. Boyer.
The audience, free to wander between several simultaneous performances on the Armory's vast open floor, seemed to become part of the choreography itself.
