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

"he extemporized a speech at the wedding"

Related terms: perform extemporization improvisation improvisation
Similar spelling:   extemporize
  extempore
  ex_tempore
  extemporarily
  extemporaneous
  extemporary
  extensor