Nobody open sourced their detection algorithm as that would just trigger a cat-and-mouse game between Suno/Udio and a detection platform (and Suno/Udio have way more VC money than you do), but plenty are being sold as a service and work very reliably.
It's trivial to vibe-code something that detects watermarked output and accidental model fingerprints. But next week the watermarks will be defeated, and the accidental fingerprints will change and ultimately disappear. It's not possible to generally solve the "To what degree is this audio AI generated?" problem, any more than it has been to solve the same problem for text and images. https://mitsloanedtech.mit.edu/ai/teach/ai-detectors-dont-wo...
The question I'm more interested in is why other music streaming services are not interested in doing this trivially easy work to get rid of spam, even if it's just for the short run as you assume it will be.
Honestly I hope that the AI filter would be much better in terms of false positive than the aforementioned one, if only because it should be easier via statistical methods.
Aside, your analogy doesn’t make sense. Horoscopes are generally not in the business of signal detection, and are usually enjoyed by the reader of the horoscope, like any other art. If you had used a sudoku solver your analogy would make a bit more sense.