ace-step

What this skill does

# ACE Step — Pro Pack on RunComfy

Tag-driven music generation, inpainting, and outpainting with StepFun-AI's **ACE Step** open-weights model. Four CLI-reachable endpoints, $0.0002–0.0003 per second of audio, up to 4 minutes per call.

[runcomfy.com](https://www.runcomfy.com/?utm_source=skills.sh&utm_medium=skill&utm_campaign=ace-step) · [ACE Step base](https://www.runcomfy.com/models/acestep-ai/ace-step/text-to-audio?utm_source=skills.sh&utm_medium=skill&utm_campaign=ace-step) · [ACE Step 1.5](https://www.runcomfy.com/models/acestep-ai/ace-step-1.5/text-to-audio?utm_source=skills.sh&utm_medium=skill&utm_campaign=ace-step) · [CLI docs](https://docs.runcomfy.com/cli/introduction?utm_source=skills.sh&utm_medium=skill&utm_campaign=ace-step)

## Install this skill

```bash
npx skills add agentspace-so/runcomfy-agent-skills --skill ace-step -g
```

## Powered by the RunComfy CLI

**Step 1 — install** (one of, see the `runcomfy-cli` skill for details):

```bash
npm i -g @runcomfy/cli         # global install
npx -y @runcomfy/cli --version # zero-install
```

**Step 2 — sign in** (or set `RUNCOMFY_TOKEN` env var in CI / containers):

```bash
runcomfy login
```

**Step 3 — generate**:

```bash
runcomfy run acestep-ai/ace-step/text-to-audio \
  --input '{"tags": "..."}' \
  --output-dir ./out
```

CLI deep dive: [`runcomfy-cli`](https://www.skills.sh/agentspace-so/runcomfy-agent-skills/runcomfy-cli) skill.

---

## Pick the right endpoint

Listed newest first.

**ACE Step 1.5 (text-to-audio)** — `acestep-ai/ace-step-1.5/text-to-audio`
> Latest ACE Step generation. **50+ language vocal support**, refined structured-lyric handling, otherwise same shape as base. Slightly higher cost ($0.0003/s vs $0.0002/s).
> Pick for: multilingual lyrics, hero-quality vocal tracks, vocal songs that need clean section structure.
> Avoid for: cost-sensitive batches where the base model is good enough.

**ACE Step (text-to-audio)** — `acestep-ai/ace-step/text-to-audio` *(default — cheap & fast)*
> Original ACE Step. Tag-driven composition, optional lyrics, 5–240 s stereo. $0.0002/s — ~27× cheaper than ElevenLabs Music.
> Pick for: high-volume drafts, background music, jingles, game loops, cost-sensitive iteration.
> Avoid for: maximally polished commercial vocal hooks — try **ACE Step 1.5** or **ElevenLabs Music** for those.

**ACE Step (audio-inpaint)** — `acestep-ai/ace-step/audio-inpaint`
> Regenerate a **time range** inside an existing track (not mask-based; uses `start_time` / `end_time` in seconds, each anchored to track start or end).
> Pick for: fix a bad chorus in the middle, swap the bridge, replace a 20 s section without re-rendering the whole song.
> Avoid for: edits that aren't time-bounded — those don't fit the schema.

**ACE Step (audio-outpaint)** — `acestep-ai/ace-step/audio-outpaint`
> Extend an existing track **bidirectionally** — add intro before, outro after, or both.
> Pick for: lengthening a 30 s draft into a 2 min cut, adding a fade-in, building a longer arrangement around an existing hook.
> Avoid for: extending a track past 4 min total — chain calls instead.

---

## Route 1: ACE Step text-to-audio (default)

**Model**: `acestep-ai/ace-step/text-to-audio` (or `acestep-ai/ace-step-1.5/text-to-audio` for the 1.5 variant)

### Schema (both variants — same shape)

| Field | Type | Required | Default | Notes |
|---|---|---|---|---|
| `tags` | string | yes | — | **Comma-separated** genre / mood / instrument tags. Drives composition |
| `lyrics` | string | no | — | Vocal content. Use section markers `[Verse]`, `[Chorus]`, `[Bridge]`. Use `[inst]` or `[instrumental]` for no vocals |
| `duration` | int | no | `60` | Audio length in seconds. **5–240** (max 4 min per call) |
| `seed` | int | no | `-1` | Reproducibility; `-1` randomizes |

**Pricing**: ACE Step $0.0002/s · ACE Step 1.5 $0.0003/s. 60 s ≈ $0.012 / $0.018; 240 s ≈ $0.048 / $0.072.

### Invoke

**Tag-driven instrumental:**

```bash
runcomfy run acestep-ai/ace-step/text-to-audio \
  --input '{
    "tags": "lo-fi hip-hop, mellow, vinyl crackle, rhodes piano, soft drums, 75 BPM",
    "lyrics": "[inst]",
    "duration": 90
  }' \
  --output-dir ./out
```

**Full vocal song with structure (use 1.5 for multilingual):**

```bash
runcomfy run acestep-ai/ace-step-1.5/text-to-audio \
  --input '{
    "tags": "indie pop, anthemic, electric guitar, driving drums, female vocal, 120 BPM",
    "lyrics": "[Verse]\nChalk on the palms, laces double-knotted\nMorning on the ridge, the sun is rising\n[Chorus]\nWe rise, we strike, we never fade out\nWe rise, we strike, we sing it loud\n[Bridge]\nSoft piano breakdown\n[Outro]\nFull band, fade",
    "duration": 60
  }' \
  --output-dir ./out
```

### Prompting tips

- **Tags do the heavy lifting** — be specific: `"lo-fi hip-hop, mellow, vinyl crackle, rhodes piano, soft drums, 75 BPM"` beats `"chill music"`.
- **Include BPM** in tags when it matters — ACE respects tempo language.
- **Lyrics with section markers**: `[Verse]`, `[Chorus]`, `[Bridge]`, `[Outro]`. Keep meter consistent across lines.
- **Instrumental shortcut**: `"lyrics": "[inst]"` or `"[instrumental]"`. Belt-and-suspenders: also say "no vocals" in tags.
- **Multilingual vocals**: ACE Step 1.5 covers 50+ languages. Write lyrics directly in the target language; tag the language too (`"japanese vocal, j-pop"`).
- **Fix the seed** for reproducibility (`"seed": 42`); use `-1` to explore variations.
- **Cheap draft → polish**: ACE Step at 5–10× lower cost is great for iterating tags before committing to a long render.

---

## Route 2: ACE Step audio-inpaint

**Model**: `acestep-ai/ace-step/audio-inpaint`
**Catalog**: [audio-inpaint](https://www.runcomfy.com/models/acestep-ai/ace-step/audio-inpaint?utm_source=skills.sh&utm_medium=skill&utm_campaign=ace-step)

### Schema

| Field | Type | Required | Default | Notes |
|---|---|---|---|---|
| `audio` | string | yes | — | HTTPS URL to MP3 / WAV / FLAC. Up to 60 min |
| `tags` | string | yes | — | Comma-separated tags steering the regenerated segment |
| `start_time` | float | no | — | Start of editable segment, in seconds (0–240) |
| `start_time_relative_to` | enum | no | `start` | `start` or `end` — anchor for `start_time` |
| `end_time` | float | no | `30` | End of editable segment, in seconds (0–240) |
| `end_time_relative_to` | enum | no | `start` | `start` or `end` — anchor for `end_time` |
| `lyrics` | string | no | — | Lyrics for the regenerated segment. Blank = model writes; `[inst]` = no vocals |
| `seed` | int | no | `-1` | Reproducibility |

**No mask** — region is defined purely by `start_time` / `end_time` (each anchorable to track start or end).

### Invoke

**Replace 20–40 s of a track with a new bridge:**

```bash
runcomfy run acestep-ai/ace-step/audio-inpaint \
  --input '{
    "audio": "https://your-cdn.example/original-track.mp3",
    "tags": "indie pop, breakdown, piano only, soft, no drums",
    "start_time": 20,
    "end_time": 40,
    "lyrics": "[inst]"
  }' \
  --output-dir ./out
```

**Anchor end relative to track end (rewrite the last 15 s):**

```bash
runcomfy run acestep-ai/ace-step/audio-inpaint \
  --input '{
    "audio": "https://your-cdn.example/song.mp3",
    "tags": "indie pop, fade, soft, ambient pad",
    "start_time": 15,
    "start_time_relative_to": "end",
    "end_time": 0,
    "end_time_relative_to": "end"
  }' \
  --output-dir ./out
```

### Tips

- **Match the surrounding tags** — if the original is "indie pop, electric guitar, 120 BPM", the inpaint segment should share enough of the tags to blend, not contrast.
- **Inpaint window is up to ~4 min** even on a 60-min source — pick a focused range, not the whole track.
- **Use `_relative_to: "end"`** to target the outro/last seconds without computing exact timestamps.

---

## Route 3: ACE Step audio-outpaint

**Model**: `acestep-ai/ace-step/audio-outpaint`
**Catalog**: [audio-outpaint](https://www.runcomfy.com/models/acestep-ai/ace-step/audio-outpaint?utm_source=skills.sh&utm_medi