simultaneity vs unification

simultaneity

noun
  • The quality or state of being simultaneous; simultaneousness. 

  • More than one complete musical texture occurring at the same time. This first appeared in the music of Charles Ives, and is common in the music of Conlon Nancarrow, and others. 

unification

noun
  • The state of being unified. 

  • Given two terms, their join with respect to a specialisation order. 

  • The act of unifying. 

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