Extend a Suno bed after runtime is known, not while the cut still moves

extend_music is not a new song. It continues a previously generated Suno track from (or near) a chosen point. You need that track's audioId from history. You cannot point it at an arbitrary MP3. It exists because a bed faded out before the outro. That sentence assumes you know when the outro is. If the cut is still moving, you do not.

Extend a music track is the job. Billed per extension, on top of the original generate. generate_music is the parent. The AI music generator is the catalog.

Runtime is a property of the locked picture

A 6-second maybe and a 14-second keeper want different tails. Extending "a bit more just in case" is how you pay for a 30-second continuation and mix 8 seconds of it. Style continuity also depends on the prompt matching the original. You will not get that match by extending a discarded generate whose mood was already a compromise.

People extend first because the song is the part they like. Then they hunt for picture. Then the picture is a different length and they extend again, or they generate a new track. The audioId you needed was on the song you will mix, which is the song that fits the keeper.

Attachment is a later step still: attach_audio_to_video in mix mode. Do not extend into a replace onto a miss.

Order

1. Lock picture duration, or accept a duration contract you will not break.
2. Generate a bed aimed at that duration.
3. If it dies early, extend from the real audioId.
4. Mix under the keeper. Duck the voice.

estimate_cost before the extension. It is a new generate in all the ways that matter for credits, even though it is a continuation in all the ways that matter for musical sense.

What this will not do

It will not rescue a track that is the wrong genre. That is a new generate_music. It will not stem-split. That is separate_music_vocals on an in-app track you are actually using. It will not grant rights to a third-party original — this path starts from a Suno generate you already made.

If you do not have the audioId, look it up. Do not start a new song to avoid the lookup. That is a second parent, and then a second extension, because you lost the first id.

FAQ

Can I extend an uploaded client MP3?

Not with this tool. Suno-generated audioId only. A client master is a different ingest and a different mix problem.

How much should I extend "to be safe"?

None, until runtime is known. Then extend the shortfall, not a round number you invented.

Should I extend before or after attaching to the video?

Before. Attach the finished-length bed once. Attaching the short version then extending the song does not update the video. You would attach again.

Does extend_music replace the original track in history?

It produces a continuation. Keep the parent id until you know which file you mixed. Mixing the wrong sibling is a real mistake.