 I think that some of what's going on with some of those Tibbett tracks is the issue of whether white people should be allowed to sing like black people and to what extent white people should be allowed to pick up a self-consciously black idiom. And it's interesting because you can hear how in the 1920s and 30s Tibbett was allowed to basically ape a black performer and that was considered at least by most people to be okay.