The Trisagion was at one time used in some parts of the West.
In churches in Gaul (France) and Spain, the so-called Aius (from Greek Hagios) was sung as one of the canticles at the beginning of the Liturgy - just after the entrance chant - followed by the triple Kyrie eleison (chanted in unison by three boys) and the Benedictus (the Canticle of Zechariah; Luke 1:68-79). It was intoned by a bishop or priest first in Greek and then in Latin, finally concluding with an Amen. The Aius was again sung, this time by all the clergy, just before the gospel. The Roman Rite got the practice of singing the Trisagion in Greek and Latin during the Good Friday Improperia (Reproaches) from the Gallican liturgies.
In the old Mozarabic rite (Spain) there was the practice of singing a version of the Trisagion just after the Gloria in excelsis was retained for Easter Sunday - followed by the Song of the Three Young Men along its use in the Improperia for Good Friday (a Roman import).
Sanctus Deus, qui sedes super cherubin, solus invisibilis.
Sanctus fortis, qui in excelsis glorificaris vocibus angelicis.
Sanctus immortalis, qui solus es inmaculatus Salvator, miserere nobis, alleluia, alleluia.
V. Dignus es, Domine, Deus noster, accipere gloriam et honorem et virtutem.
P. Sanctus fortis.
V. Quoniam omnes gentes venient et adorabunt in conspectu tuo, Domine, et dicent:
P. Sanctus immortalis.
V. Benedictio et honor et gloria, virtus et potestas tibi, Deo nostro, in saecula saeculorum. Amen.
P. Miserere nobis, alleluia.
Holy God, who sit above the cherubim, (Psalm 79 [80]:1) who alone is invisible.
Holy Mighty, who on high is glorified by the voice of angels.
Holy Immortal, who alone is immaculate Savior, have mercy on us, Alleluia, Alleluia.
V. You are worthy, O Lord our God, to receive glory, honor and virtue. (Revelation 4:11)
P. Holy Mighty.
V. For all nations shall come and shall worship in your sight, O Lord, and say: (Revelation 15:4)
P. Holy Immortal.
V. Blessing and honor and glory, virtue and power be yours, O our God, for ever and ever. (Revelation 5:13)
P. Have mercy on us, Alleluia.
After the rite was revised in the 1990s the Trisagion was sung during solemnities (the Good Friday one was struck out). There are at least two or three official forms of the Mozarabic Trisagion: one was the form described above. A variant of the above form is now the one used for the feasts of the Nativity (Year II), the Apparition (aka Epiphany; Year II), the Resurrection and Pentecost (both Years I and II). The only difference is in the final responses:
*V. Dignus es, Domine, Deus noster, accipere gloriam et honorem et virtutem.
R. Sanctus immortalis, qui solus es inmaculatus Salvator, miserere nobis, alleluia, alleluia.
V. Quoniam omnes gentes venient et adorabunt in conspectu tuo, Domine, et dicent:
*R. Miserere nobis, alleluia, alleluia. **
V. Benedictio et honor et gloria virtus et fortitudo tibi, Deo nostro, in saecula saeculorum. Amen.
R. Miserere nobis, alleluia, alleluia.
The third one (which is simply the Greek and Latin version without any tropes) is used for the feast of the Circumcision.
*Hagios o Theos,
Hagios Ischyros,
Hagios Athanatos,
eleison himas.
V. Sanctus Deus,
Sanctus fortis,
Sanctus immortalis,
miserere nobis.
R. Hagios Athanatos, eleison himas.
V. Doxa Patri ke Hyio ke Hagio Pneumati, ke nyn ai ke is tus eonas ton eonon. Amin.
R. Hagios Athanatos, eleison himas.*
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