The Soundie features "Doodles" Weaver performing a piece written by James Copp III. Thanks to Mark Cantor for spotting the theatre and running this short as part of a presentation at Cinecon 58. He's the author of "The Soundies: A History and Catalog of Jukebox Film Shorts of the 1940s," available on Amazon. The short can be seen as a post from Mark on the Facebook page The World of Soundies. It's also on the site Jazz On Film.
This 1918 vintage theatre at 3rd & Broadway was Sid Grauman's first Los Angeles operation. See the Million Dollar pages on the Los Angeles Theatres site for a history and many, many photos.