Private AI Music Creator Webapp

I want a web-based “song laboratory” that stays 100 % private to me. Inside this secure space I must be able to:

• Paste or type my own lyrics and let AI generate a full production—vocals, instrumentation and mix—around them.
• Ask the AI to craft both lyrics and music from scratch when I’m not in a writing mood.
• Upload rough recordings or demos, have the AI polish them into a radio-ready mix while preserving the original musical feel, and then compare the before/after versions.
• Create multiple variations of a piece, extend a section, or regenerate just the chorus or bridge without rebuilding the entire track.
• Stream each result in the browser, download lossless and MP3 stems, and store every version in a personal library that no one else can access.

I’m open to whichever model or API you believe suits this best—whether that’s Google MusicLM-style endpoints, Suno, OpenAI’s music tools, custom Stable Audio pipelines, or a hybrid approach—as long as licensing permits completely private use and the quality is professional.

Security and privacy are critical: the site will sit behind authentication, no public feeds, no data sharing. Clean, intuitive UI is important, but sound quality and flexibility come first.

When you reply, please outline:
1. Your relevant experience building AI-driven music or audio apps.
2. Which model(s) or service(s) you recommend and why.
3. A rough timeline with major milestones (MVP, advanced editing tools, final polish).
4. An estimated cost range for the full build plus ongoing hosting/API usage.

I’m ready to move quickly once I see a solid plan.