Someone already mentioned Freestyle Fellowship but I also think Mykah is probably the best MC to look at for that type of style. I've even seen him flip from playing the trumpet to vocally styling as if he was a human trumpet with his rhyme style and cadence.
3. "RE: examples of Emceeing approximating Jazz soloing?" In response to Reply # 0
i remember thinking that doom on madvillainy had that energy. also, i know that pharoahe has talked about the influence of coltrane and others. i can see that.