Jim,
Those 2 selections, “Aren’t you glad you’re you” and “Misty” are fine samples of jazz accordion from Leon, a mighty fine master.
I have his "I Remember Newport" album which contains those tunes.
Leon's wife Lee Morgan-Sash is playing the bass on those.
I live in Chicago and Leon lived in a suburb just north of me. One day I gave Leon a call on the phone with hopes that he would take me in as a student. He drilled me with questions to find out where my head was at (how serious I really was) and at what level of playing capability I was at.
He agreed and gave a time slot or 2 of when he would be available. I told him I would talk it over with my wife, determine the best time to schedule and get back to him.
I called him back a few days later only to get the saddest news that Leon had just passed away.
Another accordio jazz great, local to me is Don Komar who is mentioned in the link that Donny contributed above.
I studied for a short time with Don and I can tell you that the reference to Don, “Chops from hell”, is an understatement.
Currently in his 70’s, Don is swinging more with the jazz organ (B3 style) with the pedals going, although he has done some recent jazz accordion performances at local accordion clubs in the Chicago area along with his wife Anita, a very fine piano/vocalist.
If you like accordion jazz, there are other greats like Art Van Damme,
Frank Marocco .
Some jazz guys that do arranger/midi accordion styles are Mike Alongi, John Simkus, Eddie Monteiro to name a few.
Jim, thanks for sharing.