I put together a small ComfyUI workflow that turns a short music idea and a target duration into prompts for both Stable Audio 3 and ACE-Step 1.5 XL, then generates two instrumental tracks from the same plan.

In my testing, Stable Audio 3 is the more flexible option for different styles. It handled things such as retro 8-bit game music and cyberpunk BGM more naturally. ACE-Step 1.5 XL is better when the arrangement needs clearer section changes, because its instrumental structure script can describe the intro, theme, variation, build, climax, and outro separately.

The workflow uses a local text-generation node to create a strict JSON music plan. That JSON is split into the Stable Audio prompt, ACE caption, ACE instrumental structure, BPM, time signature, and key. If local prompt generation is too slow, the text-generation part can be bypassed: copy the displayed prompt to a web LLM, paste the returned JSON into the external JSON field, and keep the rest of the graph unchanged.

I recommend starting with a duration of around 2–3 minutes. Longer tracks tend to make the repeated-section problem of Stable Audio 3 more noticeable.

This workflow is super easy to use—I’ve uploaded a detailed tutorial to YouTube, so just follow the video along with this workflow to recreate the effect; please make sure to watch the full tutorial before starting to avoid common mistakes, and feel free to leave a comment if you have any questions!Resource links will be posted in the comments.