"Streamlined Swing" was directed by Buster Keaton at the lowest point in his career, when he was under contract to MGM but they refused to make proper use of his comedic talents. This film was a showcase vehicle for "The Original Sing Band", an unusual vaudeville act consisting of several young black men who play all the instruments in a band. The gimmick is that, except for one acoustic guitar, there aren't any real instruments in this band: the various bandsmen make unusual mouth noises (almost like scat-singing) to simulate the sounds of a clarinet, a saxophone, a trumpet with a wah-wah mute, and so forth. The mouth noises aren't meant to be funny; we're supposed to be impressed with the Sing Band's genuine ability to simulate the sounds of musical instruments.
Our lads in the band have got a snappy new diner but no customers, so they put on a band concert (with their nonexistent instruments) to attract a crowd, and of course there's a happy ending.
It's unfortunate that all the members of the Sing Band speak in "Yassuh" dialect, which was probably inflicted on them by some white booking agent who figured they'd be more popular with white audiences if they spoke like illiterate stereotype darkies. Also, the band's front man (the guitarist) is missing one of his front teeth, which really gives him a distressing appearance.
MGM were the richest Hollywood studio, but they obviously didn't spend much money or effort promoting the Original Sing Band. A shame, really. Buster Keaton directs this short film with proficiency but no energy. The whole film seems lackadaisical. "Streamlined Swing" deserves maybe one point out of 10, but I can't blame the men in the band for trying.