Prompted improvisation

This idea came to me in bed in the middle of the night, at least half asleep.

One composer writes a very short piece for a small ensemble. Several other composers write short works (for any or all of the same ensemble) in response. None of the composers are named until the final performance.

In my initial thought, the first piece is played just before intermission and the others respond during intermission, and their responses constitute the second half of the concert. (This is why I named it all "prompted improvisation".)

Upon later reflection, that seems impossible, so I revised it to "prompted composition" with the second set of composers given more time (24 hours? one week?) to respond. And I thought it could be named "Question and Responses".

Maybe I'll suggest this to the Los Angeles Philharmonic's Green Umbrella series.