Concerning the "heart" a couple of scriptures came to mind, although they are not in the context of musical style. In 1 Samuel 16:7, ... "Man looks at the outward appearance, but the Lord looks at the heart." In Matt. 15 the context is the Pharisees questioning Jesus, permitting his disciples to eat with unclean hands. Jesus says, ... "but the things that come out of the mouth come from the heart, and these make a man unclean. For out of the heart come evil thoughts, ... These are what make a man unclean." My understanding is that what matters is what is coming from the heart of a person. And God judges the heart.
I see what you're saying, that the hearts of man is evil. Gen. 29:11 But this, praise God, does not condemn us to hell. I agree that we are to test all things by the Word, and "some things conceivable are corrupted." To be sure! But if music that has been used in celebrations of debauchery is not acceptable then perhaps we shouldn't even have this "Christian Jazz" group forum at all! Jazz music has definitely been used in settings of debauchery, big time!
Using the same logic one might say the people who have frequented places of debauchery have no place with God. That would mean that the very people Jesus placed himself in the presence of should not have been near him. In fact if not for His redemption and grace, where would I be? If he can redeem prostitutes and tax collectors and use them for His kingdom, He certainly can redeem a style of music.
Subjectivity is certainly a real part of it. Chances are, some of the very music you find spiritually moving may have been considered blasphemous or at least strange to a worshiper a couple of centuries ago and in a different country. It's hard to accept a wide blanket statements about music when this form of expression is so subjective. I think we can make sensible musical judgments and choices based on our particular circumstances, culture, etc.
We agree that " within the context of our culture we know what is acceptable and what is corrupt."
We should be sensitive enough to know how things are perceived by people. I perform jazz in churches very often and I would never perform the "strip tease" melody. Almost everyone would immediately make the association to that known melody. But many of the rhythms and harmonies of what we play are the same sounds you'd hear in a night club, but the congregation receives it the way it's meant to be received. Either by speaking or singing I put the songs in proper context and people can sense the sincerity. But the music is technically just as rhythmic or bluesy as what you might hear in a night club. Anyway, this is my experience and this is my understanding.
LB