I already see evil doing various fun things with her TTS on stream, so here is an idea, we allow evil to control even more parameters, and give her access to a selection of song instrumentals, then on stream, she could choose to pull out a mic and then attempt to sing (or ad lib) along the instrumentals
more crucially, this would not affect karaoke streams as in normal streams evil is actively choosing what to sing, can ad lib, can go off key, and take requests directly, which i think would be quite enteratining