sentences:  The evil doctor Dr. Hartz often is first heard before he appears on screen, representing an aural intrusion “not so much an invasion of piracy as of security.”
  
  In over half of Hitchcock’s films, music is an essential component, often of fundamental importance to the plot.In "The Lady Vanishes", Gilbert is a musicologist (really an ethnomusicologist) and music teacher and Miss Froy is also a music teacher.“Hitchcock’s dependence on music, classical or popular, is also the logical outgrowth of his search for plot devices that are suggestive but that derive naturally from a situation, so that any symbolic or metaphorical value they might have is not so obtrusive as to stop the flow of action or reduce audience involvement.” Other than diegetic source music, no other music is heard during the film.