ACE-Step 1.5 Edit: The Essentials
Last updated: July 17, 2026
Covers Stem Extract, Complete Track, and Add Layer.
The ACE-Step 1.5 Edit family gives you three focused tools that work on audio you already have. Pull a single instrument out of a finished mix, build a full arrangement around a bare vocal or solo instrument, or add one new layer on top of an existing track. All three run on the full-quality ACE-Step 1.5 edit engine and keep the new parts locked to the key, tempo, and feel of your source.
Which Model Should I Use?
Start from what you already have in hand.
Model | You feed it | It gives back | Best for |
|---|---|---|---|
Stem Extract | A finished, mixed track | One isolated stem, playing alone | Remixing, sampling, karaoke and backing tracks, cleaning up references |
Complete Track | A partial: a bare vocal or a solo instrument | A full backing arrangement around it | Turning an a cappella or a riff into a produced song (Vocal2BGM) |
Add Layer | An existing track | The same track with one new instrument mixed in | Building an arrangement one part at a time |
Quick rule: a full mix and you want one part out, use Stem Extract. Just a vocal or a single instrument and you want a band around it, use Complete Track. A track that is nearly there and you want to add one element, use Add Layer.
How to Use the Models
Stem Extract
Upload a mixed track and choose the stem you want to isolate from 12 options: vocals, backing vocals, drums, bass, guitar, keyboard, percussion, strings, synth, fx, brass, or woodwinds. An optional prompt hints at the character of the stem, for example energetic female pop lead vocal. In the example below, a finished pop song goes in and the drums come out on their own.
And on an orchestral track, the string section is lifted out on its own:
Complete Track
Feed a partial recording, choose which stems to build around it, and describe the style. The model arranges parts that follow your source in key, tempo, and feel. It works best when the source carries clear melody and rhythm: the most reliable path is a clean a cappella vocal. In the example below, a solo a cappella vocal is joined by drums, bass, keys, and strings that the model generated around it, played together as the finished song.
Style prompt used: warm cinematic soul arrangement under the vocal, gentle drums, bass, electric piano, and lush strings, no added vocals
A different genre from the same approach: a soft, whispered topline turned into an electronic track, with AI synth, bass, drums, and keys built around it.
Add Layer
Upload an existing track, choose the stem to add and describe it, and optionally set a start and end time so the new part lands only where you want it. The result is your original track with the new instrument mixed in. In the example below, a ballad is shown first on its own, then again after a new synth layer was added.
Layer prompt used: lush analog synth pad supporting the ballad, matched to key and tempo
And on a pop track, an electric guitar layer added on top:
Parameters
srcAudio
Required. The audio you are editing. For Stem Extract this is a full mix, for Complete Track a bare vocal or solo instrument, for Add Layer the track you are adding to.
trackName
Stem Extract and Add Layer. The single stem to isolate or to add, chosen from the 12 instrument classes above.
completeTrackClasses
Complete Track. The set of stems to generate around your source, for example drums, bass, and guitar. Pick the instruments that fit the genre you describe in the prompt.
prompt
Describes the character or the style. Optional and short for Stem Extract, required for Complete Track and Add Layer where it sets the genre and instrumentation. Add no added vocals when you only want instruments.
repaintingStart and repaintingEnd
Add Layer only. Where the new layer begins and ends, in seconds. Leave the end at -1 to run through to the end of the track.
thinking
Complete Track and Add Layer. Lets the model plan the arrangement first for tighter musical coherence. On by default.
numOutputs
How many variations to generate, from 1 to 4, so you can pick the best take.
guidanceScale
How strictly the result follows the prompt, from 1 to 15 (default 7). Moderate values are the safe starting point. Applies on the XL base edit tier.
seed
A number that makes the first result repeatable. Leave it empty for a fresh result each run.
Use Cases
Remix and sampling: pull a clean drum or bass stem out of a track to rework or sample it.
Karaoke and backing tracks: isolate or remove the vocal to sing or play over the rest.
Songwriting from a voice memo: record a melody or a cappella idea and let Complete Track build the band around it.
Score a vocal or narration: turn a topline or spoken line into a produced piece with Complete Track.
Arranging in passes: use Add Layer to bring in one instrument at a time and keep control over the mix.
Tips for Better Results
For Complete Track, give it a source with clear melody and rhythm. A sung a cappella or a played riff works far better than a flat, sustained pad or a very short clip.
Generate a clean a cappella directly with a music model rather than isolating a vocal from a full mix. A natively generated vocal is cleaner and gives the model more to work with.
Add
no added vocalsto a Complete Track or Add Layer prompt when you only want instrumentation, so the model does not sing new parts.Match
completeTrackClassesto the genre you describe. A country prompt with guitar, bass, drums, and piano lands better than a generic instrument set.With Add Layer, use the start and end times to place a solo or a swell only in the section that needs it, rather than across the whole track.
Render 2 to 4 variations and audition them. Takes vary, and the best one is quick to spot.
Keep
guidanceScalenear the default and adjust in small steps. Pushed-up values can destabilize the result.
Known Limitations
Complete Track needs a musical source. A very short clip, a spoken-word line with little melody, or a sustained pad tends to produce a thin result. Feed it a clear sung or played phrase.
Vocal isolation quality varies. Stem Extract is strong on prominent, rhythmic parts like drums and bass. Isolating a vocal from a dense mix can be less clean, so judge the result by ear.
One stem at a time. Stem Extract returns a single stem per run, and Add Layer adds a single part per run. Chain runs to build up several.
Language and output format. The web interface exposes a vocal language selector and audio format choices (MP3, WAV, FLAC) that are not currently available through the API.
More Examples
Each model page has a set of pinned examples you can listen to and open directly: