The 1st Alleluia and Offertory for Ascension: Ascendit Deus ("God has gone up")

Ascendit Deus ("God has gone up") is the text for both the first Alleluia and the Offertory for Ascension Day.

Here's the Alleluia, sung by St. Stephen's House, Oxford:



Here's the chant score:

And here's the Offertory, sung by the Schola Cantorum Of Amsterdam Students:



Here's the chant score:

The text for both propers comes from Psalm 47; here's the JoguesChant translation (and here's an mp3 of the Offertory from their site):

God has gone up amidst shouts of joy, the Lord to the sound of the trumpet, alleluia

The Feast of the Ascension is forty days after Easter; it commemorates Christ's ascension to heaven post-Resurrection. The story is hinted at in Luke 24:31 and told fully in Acts 1:1-11; it's mentioned in Mark 16:19, too (although it's one of the disputed verses (9-20) in Mark 16). New Advent says of the Feast of the Ascension that:

The observance of this feast is of great antiquity. Although no documentary evidence of it exists prior to the beginning of the fifth century, St. Augustine says that it is of Apostolic origin, and he speaks of it in a way that shows it was the universal observance of the Church long before his time. Frequent mention of it is made in the writings of St. John Chrysostom, St. Gregory of Nyssa, and in the Constitution of the Apostles. The Pilgrimage of Sylvia (Peregrinatio Etheriae) speaks of the vigil of this feast and of the feast itself, as they were kept in the church built over the grotto in Bethlehem in which Christ was born (Duchesne, Christian Worship, 491-515). It may be that prior to the fifth century the fact narrated in the Gospels was commemorated in conjunction with the feast of Easter or Pentecost. Some believe that the much-disputed forty-third decree of the Council of Elvira (c. 300) condemning the practice of observing a feast on the fortieth day after Easter and neglecting to keep Pentecost on the fiftieth day, implies that the proper usage of the time was to commemorate the Ascension along with Pentecost. Representations of the mystery are found in diptychs and frescoes dating as early as the fifth century.

Further:

Certain customs were connected with the liturgy of this feast, such as the blessing of beans and grapes after the Commemoration of the Dead in the Canon of the Mass, the blessing of first fruits, afterwards done on Rogation Days, the blessing of a candle, the wearing of mitres by deacon and subdeacon, the extinction of the paschal candle, and triumphal processions with torches and banners outside the churches to commemorate the entry of Christ into heaven. Rock records the English custom of carrying at the head of the procession the banner bearing the device of the lion and at the foot the banner of the dragon, to symbolize the triumph of Christ in His ascension over the evil one. In some churches the scene of the Ascension was vividly reproduced by elevating the figure of Christ above the altar through an opening in the roof of the church. In others, whilst the figure of Christ was made to ascend, that of the devil was made to descend.

In the liturgies generally the day is meant to celebrate the completion of the work of our salvation, the pledge of our glorification with Christ, and His entry into heaven with our human nature glorified.

Here, from ChristusRex.org, are all the Mass Propers for Ascension, sung by the Sao Paulo Benedictines:

In Ascensione Domini
Dominica Introitus: Act. 1, 11; Ps. 46 Viri Galilæi (2m48.4s - 2635 kb) score here
Alleluia: Ps. 46, 6 Ascendit Deus (1m50.2s - 1725 kb) score here
Alleluia: Ps. 67, 18.19 Dominus in Sina (2m33.9s - 2409 kb) score here
Offertorium: Ps. 46, 6 Ascendit Deus (1m33.8s - 1469 kb MONO due to problems with my recording set) score here
Communio:
(anno A)Mt. 28, 18.19 Data est mihi (1m21.9s - 1283 kb) score here
(anno B)Mc. 16, 17.18 Signa (1m05.5s - 1027 kb)
(anno C)  Ps. 67, 33.34 Psallite Domino (59.0s - 925 kb MONO due to problems with my recording set) score here

You can read other posts about the day's propers on Chantblog as well:

• The Introit for the Feast of the Ascension: Viri Galilaei ("O men of Galilee")
• The 1st Alleluia and Offertory for Ascension:  Ascendit Deus ("God has gone up")
• The 2nd Alleluia for Ascension Day: Dominus in Sina ("The Lord is in Sinai")
• The Communion Song(s) for the Feast of the Ascension 
• The Sarum Ascension Office

And don't forget to read Full Homely Divinity's article on Ascension.

Several composers have set this text to music, including Jacobus Gallus (sung here by The Summer Singers of Minneapolis, Minnesota):



Here, The Brethren sing Jackson Berkey's setting:



And who could resist the Giuseppe Giordani version?:



Gerald Finzi's (epic!) English setting, "God is gone up," is perhaps the best known of all; it starts at about 3:20 on the video below (brought to you by the Choir of St John's College). But first, you get Stanford's Justorum Animae (from Three Latin Motets), as a bonus!