What is a body of chant of monophonic and rhythmically unmeasured style used in liturgical services of the Western Church?

It is the best-known type of a plainsong or plainchant that was dominant religious music during the Medieval Period.

It is text setting where there is a single note sung melodiously to one syllable.

It is text setting where there is a combination of two or four notes per syllable.

It is text setting where there is a blending of at least five or more notes per syllable.

It is a single unaccompanied melodic line.

He was credited to have collected and established the chants in the church services during his reign.

It is a musical symbol which designates one to four notes to a single syllable.

He innovator of solmization and staff or staves.

It helps musicians memorize and sight-sing chants.

This is the practice of singing and writing additional perfect fourths and fifths on the melodies of the chant.

It is a style of musical composition with several voice or melodies.

How many Gregorian modes or church modes?

It is the composition of parts in consideration of harmony and counter point.