The addon worked on my NVDA. I'm using the tipsy voice on the thing. I must say, it's funny to play with! Ha ha ha! Too bad it doesn't always randomize the notes it sings. Even though it gave me an incompatible addon error, it still worked! This thing is funny to mess with!
Yeah, could be just that the voices can't really handle long text. I also have dectalk for NVDA if you want that, though I'll end up posting it in the speech synthesizers forum.