How this demo works.
SongLLM is a concept: a layer that listens to a song, points at the seconds that fail, says why in a producer's words, and hands the fix to the tool you already use. This site shows that concept working on three tracks, end to end, with today's tools. It is honest about where the edges are.
What is real
| Piece | How it was made |
|---|---|
| The songs | Generated with Suno from written lyrics and style prompts. Three picked from a batch of eight for contrast: a four-minute instrumental, a rap cypher, and a whispered sketch. |
| The waveform | Peak amplitude of the actual audio, 720 bins, drawn as SVG. The dashed lines are section boundaries found by novelty analysis on chroma, timbre, and loudness, then labeled by hand against the model's reading. |
| The reading | An audio-native model (Gemini 3 Flash) heard each file and answered four questions: full technical reading, where it sags, what the hook is, and three changes. Its answers were cut for length and corrected where the file proved it wrong: a mis-heard lyric quote, an outro timestamp past the end of the track. The unedited text is on the main page under "Unedited model output." |
| Tempo and key | Tempo is measured: a comb filter over the onset envelope in 0.005 BPM steps, cross-checked by autocorrelation, with the bar line placed by hand where the kick enters. It is labelled "measured" on the page. Key is the model's call, labelled "model", or "disputed" where the chroma profile disagrees; the disagreement is shown, not resolved. |
| Loudness | Integrated loudness, loudness range and true peak from ffmpeg's EBU R128 meter on the same file you hear. Labelled "measured". Nothing in the reading's prose about loudness is a measurement unless it carries that label. |
| The bar ruler | The small ticks under the waveform are every four bars of the measured grid. The artwork videos were cut on the same grid, so every cut lands on a bar line and the loops restart in phase. |
| The notes | Edited from the model's answers, pinned to the timecodes it cited. Click one and the audio jumps there. |
| The changes | The model's three changes, each as a card: what was heard, what moves, what stays, then one instruction for the destination you pick (Suno Studio's chat bar, an ElevenLabs Music composition-plan instruction, or DAW moves). Copy and open are separate actions; nothing is sent anywhere. |
| The one that is applied | Control, change 1. The last beat before each chorus (bars 33, 67, 94 on the measured grid) is muted with a 5 ms fade and a tuned sub impact (98 Hz gliding to 49 Hz, G1) lands on each downbeat. Done as a numpy edit on the decoded bounce, encoded with ffmpeg. No EQ, no normalisation, no limiting. The A/B plays the same eight bars from both files on one clock; the revision measures 0.3 LU quieter over the excerpt because one beat is silent. The other eight changes are instructions only. |
| Corrections | Every place a human or a tool overrode the model is listed under "Corrections and provenance" on the main page: the tempo values, a mis-heard lyric quote, a timestamp past the end of the file, and the key dispute. |
What is scoped
Upload does not upload. The questions are prepared. Free text is routed by intent and the router fails closed: a question about structure, weak spots, the hook, the changes or the comparison gets the prepared answer; a question about loudness, tempo, key or length gets the measured numbers; a question this demo cannot answer (stems, stereo width, frequencies, generating or editing on request, transcription) says so and gives the reason; anything else is marked "not sure" and offered the five questions. It never falls back to the overview. The readings were produced once and stored. Nothing on this page calls a model while you use it.
What a live build does
The same questions run on your file when you upload it, with a music-understanding model behind them and the measurements taken by tools alongside. Open weights exist for exactly this task (NVIDIA's Music Flamingo, released with the UMG collaboration in January 2026), and the audio-native frontier models can already do it, as this page shows. The reading pins to the waveform with every number labelled measured, estimated or model; the changes render as cards with what they protect; the handoff opens the tool; and when your revision comes back, the A/B plays the moment it touched. Everything on this page is the interface for that.
Why the critic and not the editor
Suno Studio already edits by chat. Udio and ElevenLabs will follow. The generators own the refine loop. What none of them ship is an independent reading that points at the second and says why, in words a producer would use, and that works across every tool. Universal Music Group and NVIDIA framed their January 2026 collaboration around exactly that: understanding, discovery, and attribution. This demo is a thin, honest version of the same idea, from the outside.
Rights and disclosure
The songs are Suno outputs and are presented as such. The domain, the concept, and this demo are available to the right team. Talk to us.