The Yacht Club Boys

After years of hopeful struggle, Al Stone (Jolson) is on his way. "I'm Sittin' on Top of the World", he sings to an appreciative speakeasy crowd. But, as Al discovers, getting there is one thing. Staying there is another. Singing waiter Stone gets his huge break on a magical night when his song wows a big-time producer and a gold-digging showgirl he fancies. Broadway success and marriage follow, but sure enough, hard times are on the way. (en.wikipedia.org)

The Yacht Club Boys sing at a private party for George Mellon and his daughter. There are four of them, one of whom plays the piano, two play the guitar, and fourth plays the violin. (imdb)