Rosebrook......
You may be thinking of Hudson Shad, they do a lot of mouth music, many instruments, and were recently featured on NPR. They are terrific.
NYC group, I think, with connections to Chicago.
A cappella, 5-part, close harmony, with piano. They do ragtime, blues, jazz, lots of old German stuff.
Currently performing in Philadelphia, I think the show is called "Banned in Berlin" about Hitler's weeding out of "objectionable" performers (In this case, the "Comedian Harmonists"), who sang songs of this type in the 30s.
Do a web search on 'hudson-shad' and you'll find references, e.g., available CDs.......Tiger