AceStep 1.5 SFT Preview Audio

This is the node you put at the end of a workflow when you want to hear what you made without committing it to disk. AceStepSFTPreviewAudio takes one AUDIO input and draws an interactive waveform on the node - play/pause, click-to-seek, current-time-and-total-duration - and that's the entire feature set. It's a preview node with no outputs, which is not a bug. It's what "output node" means.

Why you'd reach for it

When you're iterating on a track - testing captions, seeds, guidance settings - you don't want a growing pile of AceStep_00037_.flac files cluttering your output folder. Preview Audio lets you evaluate renders inline, and only drop a Save Audio node in once something's actually worth keeping. It's the audio equivalent of ComfyUI's built-in preview image node, and it fills the exact same role: fast feedback loop without the file-management tax.

You'll usually run it alongside or instead of Save Audio during exploration. One nice workflow: connect both to the same audio output, keep Preview for listening and Save only when you know the render is a keeper. Since Generate passes its wires through, you can also branch a single render to multiple previews without any cost.

The waveform

The visualizer is the same one the pack's Save Audio node uses - a dark background with amplitude bars, play/pause, and click-to-seek with a time readout. For music specifically this earns its place: you can scrub to a section, hear whether the drop lands or the vocals come in clean, and move on. It's computed from the actual audio buffer, so what you see is what the sampler produced.

Nothing to troubleshoot, mostly

There's exactly one input and no configuration, so there isn't much to go wrong. A couple of practical notes:

• If the node shows no waveform, the audio wire is probably disconnected or you're looking at a stale graph - re-run the workflow.
• The preview lives in the ComfyUI frontend, so it needs the browser tab open to the running session. If you're hitting the API headless, you won't see it (use Save Audio in that case).
• Since it's an output node, ComfyUI won't execute anything downstream of it - there is no downstream. Disconnect it when you switch to Save Audio so you don't decode twice for nothing.

Install the pack once via ComfyUI Manager (search "AceStep") or git clone https://github.com/jeankassio/ComfyUI-AceStep_SFT.git into custom_nodes/, and Preview Audio appears under audio/AceStep SFT alongside the rest of the family. It's a small node with a small job, and it does it well.