In reply to:
I do not find scriptural warrant for any genre of music but I do find the descendants of Cain were the first musicians. I don't understand this to mean all music is bad but rather that God's common grace (oh no, not that term!) is at work in human creativity.

Well, were Cain descendent's the first to sing? I would say not. Since, the protoevangel of Genesis 3:15, it would have been biblical for Adam, Eve, and others to sing to the Lord (it is probable also to believe that Adam and Eve worshipped prior to this as they fellowshipped with God in the Garden). God puts a new song in the heart of His regenerate (Psa 33:1-3; 42:3, et. al.). The regenerate heart desires to glorify God.

Psa 40:3 And he hath put a new song in my mouth, even praise unto our God: many shall see it, and fear, and shall trust in the LORD.
Cain is not IMHO a model for Christian behavior! He and his would be more akin, according to their nature, to be the first Elvis’ musicians and not the first Elohim musicians. If anything I would look at the musicians of Cain as the first perversion of music, taking what God had put in the heart of His regenerate and using it to praise another. This would be in keeping with their nature.

In reply to:
Certainly human creativity can be and is misused but echoes of humanity in the image of God and His goodness to us are present nonetheless. After all, is there such a thing as any piece of music written by a Christian who would say all his motives were totally godly in producing it?

So, the songs of David (and other biblical music writers) have the wrong motivations behind them? Thus, some parts of the Word of God have the wrong motivation behind it, though God is glorified by them? confused

May God have mercy!

Reformed and Always Reforming,