STEM‑KARAOKE: CURRENT STATE

Goal: karaoke app that splits a song into stems, lets the user re‑map those stems to new instruments, and plays back the result in real‑time. You can sing over it, or play live over the stems, but the app itself does not necessarily record or export the final mixed‑down track.

WHAT IT IS

Real‑time karaoke engine that:

accepts an input track (upload or streaming proxy),
uses AI stem‑separation to split it into drums, bass, lead, vocals, etc.,
allows the user to re‑map those stems to new instruments (e.g., “French horn”, “8‑bit square”, “piano‑only”, “bass‑only”, etc.),
mixes the new stems + user voice back into a single real‑time output.

Think: “Enter Sandman on a French horn choir, you sing over it, but the app does not save the full remixed track.”

FEATURES (CURRENT IDEA)

Core modes

Single‑player stem‑karaoke: pick a song, pick your instrument mapping, sing.
Live‑only playback: no export of the remixed track, no “save” to the app.
Stem‑mute / solo modes: duck, solo, or turn off drums, vocals, bass, etc., like a standard karaoke app.

Game modes

“Opponent assigns instrumentation”: Player A picks the song; Player B picks the instrument mapping (e.g., “this song will be played on xylophone”); aber B picks the instrument mapping (e.g., “ class="strong">No‑export battle mode: ephemeral, single‑use play, no recorded “remix” saved by the app.
Optional logging of “sessions” only as metadata (song, user, instruments), not the audio itself.

WHERE WE ARE LEGALLY

Key question: is this a derivative work or not?

A derivative work is any new work based on an existing copyrighted one (remix, edit, sampled track, etc.) [web:111][web:108].
Reducing the song to stems and re‑mapping them to different instruments, then re‑playing it, is technically remix‑adjacent because you are recasting the original master in a new form, even if the app does not store it [web:108][web:111].
If the app never saves the mixed‑down er B picks the instrument mapping (e.g., “an only play it live, the system itself is closer to “runtime manipulation” or “ephemeral performance” than “distribution of a derivative track” [web:111][web:108].
If users record their own screen and upload the result, that recording is their derivative of the derivative; you are not automatically liable for that, but it still creates reputational and practical risk [web:107][web:111].

In short: the app is not “clean,” but it is significantly safer if it is live‑only and non‑exporting.

LEGAL RISK (rough, optimistic scale):

Single‑use, in‑memory playback, no‑export → ≈ 40–50% “risk” (highly sensitive to scale and who notices).
Add social‑share / export of the remixed track → ≈ 70–80% “risk” (plausible enforcement target if you grow).
License a catalog + provide “remix‑as‑service” → ≈ 20–30% “risk”, because you are operating inside the system.

APPROACHES TO MAKE IT MORE FEASIBLE

Launch in “live‑only, no‑export” mode.
- Stems are generated client‑ or server‑side, but the remixed track is never written to disk or offered as a download.
- Users can record themselves externally (phone, camera) at their own risk.
Work with a licensed catalog.
- Use standard karaoke‑style licensing for the underlying song (mechanical, possibly sync).
- Seek explicit permission from labels / artists for “remix‑style re‑mapping of stems” for specific tracks [web:111][web:98][web:109].
Frame it as a “remix‑as‑service” layer for labels.
- Partner with platforms that provide “remix‑ready” stems (e.g., AudioShake, OpenMusic AI Stem Splitter, etc.) and integrate their licensing flows [web:98][web:113].
- Charge labels a fee for enabling fan‑remixes, rather than ripping their catalog [web:98].
Keep game modes ephemeral.
- Opponent‑picks‑instrumentation is fine as long as the app itself does not save the mixed‑down track.
- Log only metadata: song, user, mode, instruments, timestamps.

WHAT TO AVOID

Exporting a “remixed” version of the original master as a downloadable file.
Making it easy for users to stream the remixed track back into social platforms via the app itself.
Marketing the app as a “remix‑distributor” or “bootleg‑master‑server.”
Using “any song” without any attempt at licensing or catalog control.

If you are tempted to do any of those, someone with a law degree probably wants to talk to you first.

SHORT‑TERM ROADMAP (FOR THE COFOUNDER)

MVP: “live‑only” stem‑karaoke.
- Stem‑separation backend (OpenMusic, LALAL, etc.).
- Real‑time mapping GUI (mute/solo/remap). No export. No save.
Playability layer.
- “Opponent assigns instrumentation” game mode, still live‑only.
- Local‑only recording allowed, but not exported through the app.
If it gains traction, negotiate a licensing spine.
- Reach out to karaoke / stem‑platform partners (AudioShake, OpenMusic, LALAL, etc.) to explore official remix‑ready catalogs.
- Build a whitelisted, permissioned track list.
Optional: label‑sanctioned remix‑as‑service.
- Labels release stems via the app; you take a rev‑share for remixing, exports, social features.
- Now you are in the “20–30% risk” bucket, assuming proper contracts.

BOTTOM LINE

This idea is not legally clean by default, but it is technically and structurally viable if you:

keep the app live‑only / non‑exporting at first,
avoid positioning it as a “remix‑distributor,”
and treat licensing as a first‑class architecture constraint, not an afterthought.

If you behave like a respectful, label‑adjacent remix layer, the odds of this actually becoming a real product are decent. If you try to be a “pirate‑engine‑first,” odds drop fast.

REFERENCESer B picks the instrument mapping (e.g., “s="unbold"> [web:98] AI‑powered stems and derivative‑work licensing. [web:108][web:111] What counts as a derivative work (remix, edit, etc.). [web:84][web:113] AI stem‑separation karaoke workflows. [web:109] How to remix a song legally (or not).