"We cheerfully maintain the old traditions made in the Church for the sake of usefulness and peace. We interpret them in a more moderate way and reject the opinion that holds they justify. Our enemies falsely accuse us of setting aside good ordinances and Church discipline. We can truly declare that the public form of the churches is more fitting with us than with the adversaries. If any one will consider it in the right way, we conform to the canons more closely than the adversaries. Among the adversaries, unwilling celebrants, and those hired for pay, and very frequently only for pay, celebrate the Masses. They sing psalms, not that they may learn or pray, but for the sake of the service (as though this work were a service) or, at least, for the sake of reward. Among us many use the Lord's Supper every Lord's Day. They do so after they have been first instructed, examined, and absolved. The children sing psalms in order that they may learn. The people also sing so that they may either learn or pray." (emphasis mine) —Apology XV, 38-41, Concordia: A Reader's Edition of the Book of Concord
What is the order of the Divine Service at Luther's time in which songs are sung so the laity may "either learn or pray"? On page 219 of "Concordia The Lutheran Confessions: A Reader's Edition of the Book of Concord (2nd. Ed.), Luther's form of the mass from 1523 is listed as follows,
a. Sursum Corda, "The Lord be with you..." and Preface
b. Words of Institution (preferably sung)
c. Sanctus, "Holy, Holy, Holy..." and Benedictus, "Blessed is He who comes..." (with elevation of body and blood)
d. The Lord's Prayer
e. Pax, "The peace of the Lord..."
f. Agnus Dei, "Lamb of God..." (sung by choir during administration)
g. Communion (antiphonal Psalm, during which priest communes first, then people)
h. Benedicamus, "Let us bless the Lord" (optional Alleluia in place of "Ite missa est," "Go; it is the dismissal")
i. Aaronic Benediction, "The Lord bless you and keep you..."
Where would one widely depart from the form of the Divine Service as adopted by Luther in 1523 and why? It is obvious from the Apology that at least the songs were sung as a teaching device or for prayer and what is striking is that the full form of the liturgy is most importantly Christ centered, but is also catechetical. We are truly fed in the Divine Service with Christ's word and His body and blood. Our faith is strengthened as we corporately receive from the hand of God the forgiveness of sins. We also are taught in the Divine Service that we may know our Lord. The songs are not entertainment, but teaching devices for the laity.
Melanchthon writes, "We cheerfully maintain the old traditions made in the Church for the sake of usefulness and peace." Today such a laudable idea appears foreign to congregations who invoke change in the name of "Christian freedom." It is refreshing to read in the Apology that the concern for the Divine Service was to preserve what was good and not reject, wholesale, the liturgy because it was Roman Catholic in origin, or "looks too Roman Catholic." More importantly, the form of worship was conserved because of its usefulness; here again, because it teaches us about Christ. The focus is certainly on maintaining pure doctrine in the congregations. There is no talk of devising a form of the Divine Service that is focused on attracting unrepentant sinners. Why? Because the Divine Service is conceived for sinners who thirst after the righteousness of God. It is already designed with Christ at the center coming to us with the forgiveness of sins. The Gospel is proclaimed from start to finish in the "traditional" liturgy. Why would anyone want something different?