extempore vs unrehearsed

extempore

adj

  • Carried out with no preparation; impromptu. 

noun

  • Something improvised. 

adv

  • Without preparation; extemporaneously. 

unrehearsed

adj

  • Not rehearsed 

How often have the words extempore and unrehearsed occurred in a corpus of books? (source: Google Ngram Viewer )