Greyduster good for you if you can play those tunes. I had a phase about 15 years ago, trying to play Gershwin on the piano. First I bought a book which was technically impossible for me, then a simplified one - managed a few slow ones (How long has this been going on? , Who Cares? Some Day he'll come along).I've heard Walking the Dog but can't play it. Can't play anything much now, arthritis. And laziness.
Luckygirl that first link has an opera singer singing Summertime - I agree, it doesn't sound right. Ella Fitzgerald sings it better, imo.