congruency vs simultaneity

congruency

noun
  • The state of being congruent 

  • The quality of agreeing; being suitable and appropriate 

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. 

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