I'm not sure if he's the "greatest" but he's probably the best I've heard. 
To me, his single most impressive attribute is his solo instrument playing. His Clarinet riffs sound like a Clarinet, his trumpet riffs sound like a trumpet, etc. 
I've heard lots of arranger users who play all sounds like a piano and that just doesn't work so well. 
He also has plenty of chops both technique and taste wise...
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Bill in Dayton
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Bill in Dayton