This may seem like slight entertainment, and of course it is. But I am recommending it as must viewing until I find an earlier example with this structure.
The setup is simple enough: it is explicitly a self-aware movie. In fact Kyser comes on at the end and assures the audience that Lorre, Karloff and Lugosi aren't really murders. Within that are several performances of the band, performances I assume are similar to what they did in non-movie-land. Two performances.
Added to that in a clever way is a third. For this you need some background.
From about 1880 to 1910, many North Americans were spiritualists. Yes, about as many as today call themselves evangelists, the movement that displaced spiritualism. The rapidity of the change is breathtaking in a sociological context and interesting in itself. By the thirties, the "next" generation was making serious fun of spiritualism, usually in terms of uncovering a fake séance.
I've found several earlier fake séance movies, but they are all in the context of detective movies. That's another story all together. Superficially, they look like the fakery in this movie: a secret room, microphones, special effects, gullible participants holding hands.
But this is the first I think that references it as a performance. A lot flows from that tipping point on both sides: movies and the religious show.
Three layered performances, here.
Ted's Evaluation -- 3 of 3: Worth watching.