listen vs tune in on

listen

noun
  • An instance of listening. 

verb
  • To pay attention to a sound or speech. 

  • To expect or wait for a sound, such as a signal. 

  • To accept advice or obey instruction; to agree or assent. 

tune in on

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