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Hyla chrysoscelis/Hyla versicolor
The gray treefrog, Hyla versicolor, has a slower and much more mellow trill than the Hyla chrysoscelis, but are otherwise undistinguishable. It has only been found in three counties in the Fort Knox area of Kentucky. So I would go with the Cope's Gray Treefrog on this one.
The two gray tree frogs found in Kentucky are identical in appearance and in many cases cannot be told apart except for their calls.