mixing vs simultaneity

mixing

noun
  • The act, or the result of making a mixture. 

adj
  • Of a stochastic process, to be asymptotically independent (in a precise mathematical sense). 

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