1. Low-noise applications. I’d naively expect the 555 to be less noisy than a clocked digital microcontroller, though it’s been awhile since I’ve worked in this space.

2. Low power applications. How does latent power draw compare between a 555 and a typical low power microcontroller?

Then take a look on https://yusynth.net at some of the VCF designs, and build one of them.

You won't have a synthesizer, you'll have some crazy homebrew drone machine that you can make scary movie sountracks with.