The fact other Christians esteem the "back-beat" as evil doesn't mean the Bible does. As with you, I have the Scriptures as my final authority.

There are no piano's mentioned specifically either. So, not all instruments are mentioned, but most "instrument families" are and that should suffice.

I believe my "faulty analogy" is not so faulty. What makes music worldly/fleshly? Is it the music itself or the composer/arranger/performer/spirit behind it?