Thanks to Andrew Brown on his release of Gold Star material, Devil in the Bayou, we know that it was Choate on his birth certificate, which is commonly pronounced Shoat in Vermilion parish. He could date when the man started using the name Choates instead (on his social security card application), but not why.
Some recordings feature various piano accordion players, but not what we call the French accordion.
Nick, if you know Harry's Basile Waltz, compare it with Valse a 'Tit Maurice! Aldus did it ('Tit Maurice). Terry Clement did it first. Check my Web site for Clement Brothers' version.
About Harry Choates, there is a bio about him in "Accordions, Fiddles, Two-Steps, and Swing" by Ryan Brasseaux and Kevin Fontenot (editors). This book highlights the careers of many Cajun musicians and as Big Nick mentioned, Harry Choates lived hard and died young...too bad because he was such a talent. Harry Choates is cited by Hadley Castille (and others) as being a huge influence. If you get the chance, ask Mr. Hadley about Harry Choates because I think that he has some good stories about him.