Frank Sinatra was probably voiced by a member of The King's Men, a group that had performed for other Warner Brothers shorts.
The baritone rooster is frequently identified as a caricature of Vaughn Monroe. However, "Shortenin' Bread" was a big hit for Nelson Eddy not Monroe, making it more likely he was the intended target of the parody.
The caricatured celebrities are, in order of appearance: The Crooner: Frank Sinatra; "Shortenin' Bread": Nelson Eddy; "September in the Rain": Al Jolson; "Lullaby of Broadway": Jimmy Durante; "Blues in the Night": Cab Calloway; The Old Groaner: Bing Crosby.
The only Porky Pig cartoon to be nominated for an Academy Award.