This is Sinatra and Louie Armstrong performing it on an episode of Sinatra's TV show, around 1957:
Here are Frank, Dean, Sammy, and........Johnny Carson (he was a last minute replacement for Joey Bishop who was unable to attend) at a 1965 benefit for the St. Louis Dismas House. "The Birth of the Blues" was the closing number. Carson was given the difficult bridge section to sing. Makes sense.
a whippoorwill's song
And all this time, here I am thinking it emerged in African-American communities of the southern U.S. from spirituals, work songs, field hollers, shouts and chants, and rhymed English and Scots-Irish narrative ballads.