I've had to place this together from many sources over a couple years. the program was sponsored by the Davis Perfection Bakery and was a variety stage revue show. There were skits, comedy and a little music of course. If you look carefully, you can see the bakery logo on that truck in the pic.
The house band "The Optimistic Do-Nuts" included Isaac McVea, who unwittingly became the first black radio host in Los Angeles. His son Jack McVea played ukulele in the same band. The program began in the early 1920s. In the cast was a little known actor Sam McDaniel, who played a preacher character, Deacon McDaniel in 1926.
In the book Don't Touch That Dial, author J. Fred Mac Donald makes a single short reference to the program
"Although they did not flourish on radio, black comedians were also an ingredient of early broadcasting... Thus Ernest Whitman and Eddie Green appeared as a "coon act" on the Maxwell House Show Boat Program in it's first season on NBC. Hattie McDaniel brought her Mammy personality from the Optimistic Doughnut Hour over KNX (Los Angeles) in 1932 to the Show Boat series in the early 19302. "Hattie McDaniel was a regular on the program as the character Hi-Hat-Hattie. Today she is better remembered for playing a similar Mammy character in the movie Gone With The Wind. It's off topic but of the 300 films she appeared in before her death in 1952, she only got credit for about 80. On the upside she's the only person who has two stars on the Hollywood Walk of Fame, and was on a postage stamp. But I dwell here because her career began singing with the Melony Hounds on station KOA-AM in Denver.
Other guests on the Optimistic Doughnut Hour included an unlikely list of people: Morey Amsterdam, Minnie Pearl, Willie Best. Hattie McDaniel joined the show in 1931 after her brother Sam McDaniel got her an audition. Her success on the program led to her own show Hi Hat Hattie and Her Boys. She did a saucy late vaudeville comedy and sang. The boys of course were just Sam McVea's Jazz band.
The Davis Perfection Bakery who sponsored all this was just a bakery. Actor Dalton Trumbo worked there briefly as a bread wrapper . The bakery was big enough to appear on a 1932 map of L.A. near Los Angeles City Hall on Temple Street. Another souce lists it at the intersection of 1st. and Beaudry and another location in Sacramento. It was probably a regional chain since it was dolling out cash for radio ads.