1998-jul-05 Dies Domini
http://www.vatican.va/holy_father/john_paul_ii/apost_letters/documents/hf_jp-ii_apl_05071998_dies-domini_en.html
29. [...] Recited or sung, the Creed declares the baptismal and Paschal character of Sunday, making it the day on which in a special way the baptized renew their adherence to Christ and his Gospel in a rekindled awareness of their baptismal promises. Listening to the word and receiving the Body of the Lord, the baptized contemplate the Risen Jesus present in the "holy signs" and confess with the Apostle Thomas: "My Lord and my God!" (Jn 20:28).
50. Given the nature of Sunday Mass and its importance in the lives of the faithful, it must be prepared with special care. In ways dictated by pastoral experience and local custom in keeping with liturgical norms, efforts must be made to ensure that the celebration has the festive character appropriate to the day commemorating the Lord's Resurrection. To this end, it is important to devote attention to the songs used by the assembly, since singing is a particularly apt way to express a joyful heart, accentuating the solemnity of the celebration and fostering the sense of a common faith and a shared love. Care must be taken to ensure the quality, both of the texts and of the melodies, so that what is proposed today as new and creative will conform to liturgical requirements and be worthy of the Church's tradition which, in the field of sacred music, boasts a priceless heritage.
55. [...] Voicing an awareness widespread in the Church, Saint Augustine describes the joy of the weekly Easter: "Fasting, is set aside and prayers are said standing, as a sign of the Resurrection, which is also why the Alleluia is sung on every Sunday". (102)
