In his preface to Georg Rhau’s Symphoniae iucundae, Martin Luther extolled the value of music, especially when it is used to praise our Creator.
I would certainly like to praise music with all my heart as the excellent gift of God which it is and to commend it to everyone.…
Music touches emotions
Next to the Word of God, music deserves the highest praise. She is a mistress and governess of those human emotions—to pass over the animals—which as masters govern men or more often overwhelm them. No greater commendation than this can be found—at least not by us.
Whether you wish to comfort the sad, to terrify the happy, to encourage the despairing, to humble the proud, to calm the passionate, or to appease those full of hate…, what more effective means than music could you find?
Music is used by the Spirit
The Holy Ghost himself honors her as an instrument for his proper work when in his Holy Scriptures he asserts that through her his gifts were instilled in the prophets, namely, the inclination to all virtues, as can be seen in Elisha [2 Kings 3:15].
On the other hand, she serves to cast out Satan, the instigator of all sins. [That] is shown in Saul, the king of Israel [1 Sam. 16:23].
Music paired with the Word
Thus, it was not without reason that the fathers and prophets wanted nothing else to be associated as closely with the Word of God as music. Therefore, we have so many hymns and psalms where message and music join to move the listener’s soul….
After all, the gift of language combined with the gift of song was only given to man to let him know that he should praise God with both word and music, namely, by proclaiming [the Word of God] through music and by providing sweet melodies with words.
Source: Luther’s Works, Volume 53, page 321