Extend Music · V6

Songs from an API come back short, and "more of that" is the most common next request. This node carries a track further from a point you pick, using the V6 tier - the live one, now that KIE's docs mark V5 and V5.5 as discontinued.

The one thing to internalise: audio_id is a Suno track identifier. It comes back in a generation's outputs, not from your filesystem. That makes the natural pattern generate-then-extend inside one graph. If your source is a file you own, use Upload And Extend Audio instead - it takes a URL, and mixing the two up is the classic first mistake with this pair.

There's a second, subtler reason to keep tiers matched while extending: a different Suno generation is a different vocal character. Extending a V6 track with a V5 node gives you an audible seam. Same tier, same singer.

How it works

The pack builds node classes from KIE's official API docs at startup, one per documented model version, so V6 is baked into this class and there's no dropdown to change. The node assembles the documented request body, submits it to KIE's task endpoint (envelope model ai-music-api/extend, inner model V6), then polls KIE's record-info endpoint every couple of seconds with backoff until the task succeeds. It downloads the resulting mp3 and returns a native ComfyUI AUDIO; a failed task raises with the task id and the provider's message.

The inputs that matter

• audio_id - the track to extend. Source audio alone is enough to generate, per the docs; everything else is steering.
• prompt - used as lyrics only when lyrics is empty, and it must not be set when instrumental is true.
• continue_at - seconds, default 60, and the docs' constraint is precise: greater than 0 and less than the total duration of the source. This is the field that determines whether the join sounds like a continuation.

Then the steering controls: style (keep it aligned with the original - this tier allows up to 1000 characters), title, negative_tags, vocal_gender, style_weight, weirdness_constraint, audio_weight, persona_id / persona_model (Suno's reusable style or voice persona - the docs scope these to V5, V5.5, V6 and the V6 variants), lyrics (up to 5000 characters on V6, and it wins over prompt), variety (0–4), instrumental (false by default here), timeout_seconds (1200) and callback_url (leave empty).

Outputs: audio, url, all_urls_json, task_id, raw_json, credits_consumed, credits_left. Extension produces a new track rather than editing the original, so all_urls_json is where the full set lives, and keeping task_id around lets you chain further extensions.

Installing

ComfyUI Manager, search "KIE Nodes Next" - the README still describes registry publication as prepared rather than live, so the manual route is the one that reliably works:

cd ComfyUI/custom_nodes
git clone https://github.com/felipederosilva/ComfyUI-KIE-Nodes-Next
pip install -r ComfyUI-KIE-Nodes-Next/requirements.txt

Restart and set the key once at Settings → KIE.ai Nodes Next → Connection. It's validated against KIE before it replaces a working key, the frontend only ever sees a masked fingerprint, and KIE_API_KEY overrides the saved key for headless installs. Four small dependencies, no torch, no model files, no VRAM.

Where people get burned

• A URL in audio_id. The node submits, KIE rejects. Files belong on the Upload And Extend node.
• continue_at outside the track. Chosen too late it fails; chosen too early you get a re-sung chorus. Check the duration.
• No key configured → an explicit error naming the settings path.
• A timeout is not a cancellation. Polling stops at timeout_seconds; the job may still finish on KIE's side, and you've paid for it either way. Check credits_consumed before running again.
• Mixed-release installs are refused at import. Version and generated-node build must match; if they don't, delete the folder and reinstall.
• Tier mismatch across a chain. If you extend, then extend the extension with a different tier's node, expect a change in voice.

Extend in short hops rather than one long jump. Fifteen seconds twice usually joins better than thirty once, and if the seam is bad you've only lost one cheap call finding out.