listen vs pick up on

listen

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. 

noun
  • An instance of listening. 

pick up on

verb
  • To notice, observe, learn, or understand, especially something otherwise overlooked. 

  • To adopt a practice in which others already engage. 

  • To continue or build upon (for example, a task, analysis, or narrative), beginning from a point at which someone has previously stopped. 

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