behind the scenes vs under the radar

behind the scenes

prep
  • In secret; out of public view. 

  • behind the scenery and stage area; backstage; among the actors; during the production or rehearsal 

adj
  • Being or working out in secret or out of public view. 

  • Divulging or reporting hidden workings. 

under the radar

prep
  • Without attracting notice; in an undetected or secretive manner. 

How often have the words behind the scenes and under the radar occurred in a corpus of books? (source: Google Ngram Viewer )