Improvisation Common

a creation spoken or written or composed extemporaneously (without prior preparation)

"The comedian's entire set was pure improvisation, as he made up every joke in response to the audience's laughter."

an unplanned expedient

"When the bridge collapsed, our only option was to use a rope and some debris as an improvisation to cross the gap before dark."

a performance given extempore without planning or preparation

"The band's sudden shift into jazz relied entirely on the musicians' skill at improvisation, as they created a cohesive melody from scratch during the live set."

The act or art of composing and making music, poetry, and the like, extemporaneously

"The jazz band relied on their collective improvisation to create a stunning melody without any prior rehearsal."