concurrentness vs simultaneity

concurrentness

noun
  • The state or quality of being concurrent. 

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 concurrentness and simultaneity occurred in a corpus of books? (source: Google Ngram Viewer )