simultaneity vs synchroneity

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. 

synchroneity

noun
  • The state or characteristic of being synchronous or synchronized. 

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