emergency vs impromptu

emergency

noun
  • Arising from or used in an emergency. 

  • A situation which poses an immediate risk and which requires urgent attention. 

  • An individual brought in at short notice to replace a member of staff, a player in a sporting team, etc. 

  • The department of a hospital that treats emergencies. 

impromptu

noun
  • Any composition, musical or otherwise, that is created on the spot without preparation. 

  • A short musical composition for an informal occasion often with the character of improvisation and usually to be played solo. 

adj
  • Improvised; without prior preparation, planning or rehearsal. 

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