tremolo vs whirr

tremolo

noun
  • A variation in the volume of a note or a chord, evoking a tremor or quiver. 

  • The device in an organ that produces a tremolo effect. 

  • A rapid repetition of the same note, or an alternation between two or more notes. It can also be intended to mean a rapid and repetitive variation in pitch for the duration of a note. It is notated by a strong diagonal bar across the note stem, or a detached bar for a set of notes (or stemless notes). 

whirr

noun
  • A sibilant buzz or vibration; the sound of something in rapid motion. 

  • A bustle of noise and excitement. 

verb
  • To make a sibilant buzzing or droning sound. 

  • To cause (something) to make such a sound. 

  • To move or vibrate (something) with a buzzing sound. 

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