A Dictionary of Music and Musicians/Quintus
QUINTUS (the Fifth). The Fifth Part in a composition for five Voices: called also Pars quinta and Quincuplum. In Music of the 15th and 16th centuries, the Fifth Part always corresponded exactly, in compass, with one of the other four; it would, therefore, have been impossible to describe it as First or Second Cantus, Altus, Tenor, or Bassus.
[ W. S. R. ]