Gaudeamus
Josquin des Prez:
Kyrie   Gloria   Credo   Sanctus   Agnus Dei
Edition:  Josquin des Prez, Werken, ed. Albert Smijers, (Amsterdam: Vereniging voor Nederlandse Muziekgeschiedenis, 1927-69), I. i. 57-79 (Aflevering 12, Missen 3).

Gaudent in celis
Anonymous (lost).
Copied at the Collegiate Church of the Holy Trinity, Tattershall, in 1496/97. See: Andrew Wathey, “Lost Books of Polyphony in England: A List to 1500,” RMA Research Chronicle, 21 (1988): 1-19, at 10.

Gentil madona
Anonymous (?Dufay, or someone consciously emulating his late style):
Kyrie   Gloria   Credo   Sanctus   Agnus Dei
Source:  TrentC 91, fols. 247v-256v (c.1475-78).
NB. The Benedictus has the trope Marie filius in the top voice, confirming the Marian destination of this setting.

Ghy syt die wertste boven al
Johannes Ghiselin-Verbonnet:
Kyrie   Gloria   Credo
Edition:  Johannes Ghiselin-Verbonnet, Opera omnia, ed. Clytus Gottwald, 4 vols., Corpus Mensurabilis Musicae, 23 (American Institute of Musicology, 1961-68), 3: 66-81.

Gracioulx et biaulx
Jacob Obrecht:
Kyrie   Gloria   Credo   Sanctus   Agnus Dei
Edition: Jacob Obrecht, New Obrecht Edition, gen.ed. C. J. Maas, 18 vols. (Utrecht: Vereniging voor Nederlandse Muziekgeschiedenis, 1983-1999), 13: 45-92.

Gratieuse plaisante munière
Johannes Ghiselin-Verbonnet:
Kyrie   Gloria   Credo   Sanctus   Agnus Dei
Edition:  Johannes Ghiselin-Verbonnet, Opera omnia, ed. Clytus Gottwald, 4 vols., Corpus Mensurabilis Musicae, 23 (American Institute of Musicology, 1961-68), 3: 1-34.

Grecorum
Jacob Obrecht:
Kyrie   Gloria   Credo   Sanctus   Agnus Dei
Edition: Jacob Obrecht, New Obrecht Edition, gen.ed. C. J. Maas, 18 vols. (Utrecht: Vereniging voor Nederlandse Muziekgeschiedenis, 1983-1999), 5: 1-33.

Gross senen
Anonymous:
Kyrie   Gloria   Credo   Sanctus   Agnus Dei
Source:  TrentC 89, fols. 26v-41r (c.1468).