Luther wanted worship to be conducted in a known language (following Paul) because worship that is unintelligible cannot be edifying. As Paul said: “For if I pray in a tongue, my spirit prays but my mind is unfruitful. What am I to do? I will pray with my spirit, but I will pray with my mind also; I will sing praise with my spirit, but I will sing with my mind also.” (1 Cor. 14:14–15)
Luther therefore translated prayers and hymns from Latin into German. But there is no evidence at all that Luther ever said that worship had to be conducted in contemporary-sounding musical idioms. To the contrary, what evidence exists suggests that Luther believed in what we now call sacred music—music that is deliberately and self-consciously different from other forms of music. He and others of his generation often wrote new musical tunes, for the distinctive purpose of accompanying hymns. And at any rate, vernacular and contemporary mean different things, and therefore an argument for one is no argument for the other.
Luther did not argue that a prayer or hymn had to sound contemporary; he argued that it had to be intelligible, and therefore conducted in the vernacular language of a given culture. It is simply historically false to recruit Luther into this discussion. Yet the fact that he manifestly did consult earlier liturgies and translate portions of them into German is evidence that he exhibited no concern for that which was contemporary, and a very self-conscious concern to conserve and preserve forms from the past. His concern was for intelligibility, not contemporaneity.
T. David Gordon in 'Why Johnny Can't Sing Hymns: How Pop Culture Rewrote the Hymnal' , cited in this review.