It is found in late-century manuscripts, including the Chigi codex (c. 1498–1508),[2] and was published in 1539,[3] 42 years after the composer's death in 1497.
The work's name reflects the fact that it may be sung in any of the Dorian, Phrygian, Lydian or Mixolydian modes.
This is made possible by writing the music without clefs or key signatures, allowing the singers to assume those suited to the chosen mode.
[4] This unusual and complex idea has led the musicologist Fabrice Fitch to describe the mass as "the work chiefly responsible for Ockeghem's reputation as an artful pedant".
[4][note 1] According to the musicologist Richard Turbet, this makes the Mass easiest to sing in the Phrygian mode and successively more difficult in the Misolydian, Lydian and Dorian modes.