improvize
1. [ verb ] (music) perform without preparation
Synonyms: improvise extemporise extemporize ad-lib
Examples:

"he extemporized a speech at the wedding"

Related terms: perform extemporization improvisation improvisation
Similar spelling:   improvise
  improve
  improvised
  improvident
  improver
  improved
  improving
  improvidence
  improvable
  improvement
  impropriety
  improper
  improperly
  improbable