OK, good people. Here's the lowdown! Amazing Grace is indeed a pentatonic tune. If you want to play it in C you can do so on a C harp (first note 3-blow), a G harp (first note 4-blow) or an F harp (first note 4-draw), without bending. I prefer a low F harp meself! Here's another thing to try. Take a G harp (which is what I happen to have to hand). You can play Amazing Grace in G (first position, first note 3-blow), in D (second position, first note 4-draw) or in C (twelfth, or first-flat, position, first note 4-blow). This is a very good thing to do because it gets you playing a melody in something other than first position, the key of the harp, and that will make you a far more flexible player. Similar tunes to try in this way are Dirty Old Town and Auld Lang Syne, both pentatonic tunes.

Going back to Amazing Grace, if what you have happens to be a C harp, you can play it in C (first position, first note 3-blow), G (second position, first note 4-draw) or F (twelfth, or first-flat, position, first note 4-blow). And nothing I've said requires a bend!