Euouae

Euouae or Evovae is an abbreviation used in Latin psalters and other liturgical books to show the distribution of syllables in the differentia or variable melodic endings of the standard Psalm tones of Gregorian chant. It derives from the vowels in the words "saeculorum Amen" of the lesser doxology or Gloria Patri, which ends with the phrase In saecula saeculorum, Amen. In some cases the letters EUOUAE can be further shortened to E----E. A few books of English chant (notably Burgess & Palmer's The Plainchant Gradual, Wantage 1962) make use of 'oioueae' for the equivalent phrase "World without end. Amen."