beep vs undertone

beep

noun
  • A short, electronically produced tone. 

  • A message sent to a pager device. 

  • The sound produced by the horn of a car, or any similar sound. 

verb
  • To sound (something that makes a beep). 

  • To contact (someone via) a pager device. 

  • To telephone a person, only allowing the phone to ring once, in order to request a call back. 

  • To produce a beep. 

  • To have sexual intercourse with - referring to the bleep tone used to censor obscene words in broadcasts 

undertone

noun
  • An auditory tone of low pitch or volume. 

  • A pale colour, or one seen underneath another colour. 

  • A low state of the physical faculties. 

  • An implicit message perceived subtly alongside, but not detracting noticeably from, the explicit message conveyed in or by a book, film, verbal dialogue or similar (contrast with overtone); an undercurrent. 

verb
  • To accompany as an undertone. 

  • To say or speak in an undertone. 

  • To present as less important, noticeable or prominent. 

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