duet vs span

duet

verb
  • To perform (sing, play, etc.) as a duet. 

  • (of two people) To say at the same time, to chorus. 

  • To perform a duet. 

  • To communicate (warnings, mating calls, etc.) through song. 

noun
  • A musical composition in two parts, each performed by a single voice (singer, instrument or univoce ensemble). 

  • A song composed for and/or performed by a duo. 

  • A pair or couple, especially one that is harmonious or elegant. 

span

verb
  • To fetter, as a horse; to hobble. 

  • To extend through the distance between or across. 

  • To extend through (a time period). 

  • To measure by the span of the hand with the fingers extended, or with the fingers encompassing the object. 

  • To generate an entire space by means of linear combinations. 

noun
  • The space of all linear combinations of something. 

  • A portion of something by length; a subsequence. 

  • A small space or a brief portion of time. 

  • The spread or extent of an arch or between its abutments, or of a beam, girder, truss, roof, bridge, or the like, between supports. 

  • The time required to execute a parallel algorithm on an infinite number of processors, i.e. the shortest distance across a directed acyclic graph representing the computation steps. 

  • wingspan of a plane or bird 

  • The length of a cable, wire, rope, chain between two consecutive supports. 

  • Any of various traditional units of length approximating this distance, especially the English handspan of 9 inches forming ⅛ fathom and equivalent to 22.86 cm. 

  • A pair of horses or other animals driven together; usually, such a pair of horses when similar in color, form, and action. 

  • A rope having its ends made fast so that a purchase can be hooked to the bight; also, a rope made fast in the center so that both ends can be used. 

  • The full width of an open hand from the end of the thumb to the end of the little finger used as an informal unit of length. 

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