I heard an interesting show on PBS once - i think it was "Schickelie's Mix", where he expounded on the subject of the pentatonic scale, and mentioned a few songs that were written for it. I can't remember now, but think that "Amazing Grace" was one of them, much to my surprise.

Perhaps you can go to the NPBN Website (National Public Broadcasting) and see if they have an archive site for Peter Schickelie (I'm not at all sure about the spelling). He's a really entertaining, as well as educational Musician.

Our Daughter has two Indian "Love-flutes", one of which we made and one she bought from a Maine Artisan, both of which are five-holers, and I assume pentatonic. She makes some lovely, haunting music on them, and can imitate many wild bird calls, including the loon, and incorporate them into her music. I'm not all that familiar with the scale, but would like to learn more about it and perhaps try composing in it.

Thanks for asking, and I'll be keeping track of this thread for a while in hopes of learning with you. We have quite a few very knowledgeable Musicians in here and I have little doubt but that we will soon be amply edified!