That sounds like a lovely project, and the idea of using sine curves to create gentle tones is clever. The phrasing you’ve chosen so far is soothing, but a few tweaks could make it even smoother. For example, instead of “cooking up an AI,” say “developing an AI,” because “cooking up” feels a bit informal. Also, “gentle sine curves and soft harmonics” could be tightened to “gentle sine waves and soft harmonics,” which rolls off the tongue better. Overall, you’re on the right track—just polish a little, and it will feel truly lullaby‑like.