improvisation vs penning

improvisation

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

  • That which is improvised; an impromptu. 

  • Musical technique, characteristic of blues music. 

  • The act of improvising, acting or going about something without planning ahead 

penning

noun
  • Writing; literary composition. 

  • An old currency unit, the Swedish penning. 

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