You generated a chill house track at “120 BPM” in Suno. The intro feels right. Around the second verse the kick speeds up. By the outro you are at 128-ish, and the energy feels wrong — not in a good rising-tension way, just a wobbly drift. Pull the file into a DAW with tempo detection and you can see the BPM curve rising over time. This is one of the most common Suno/Udio complaints, and it is almost always a prompt-structure issue plus a model tendency to add energy as a song progresses. The model does not have a metronome — it has a feel — and “feel” drifts.
Common causes
Ordered by frequency.
1. Model interprets “120 BPM” as a style suggestion, not a constraint
Suno and Udio do not run a metronome at the BPM you write. They infer rhythm from style cues. “120 BPM house” produces something in the house tempo range but not pinned to 120.
How to spot it: Use a DAW or tempo detection on the generated file. If BPM drifts ±5-10 across the song, the model never locked tempo.
2. Section prompts have conflicting energy levels
A prompt like “verse: chill / chorus: explosive / bridge: euphoric drop” tells the model each section escalates. The model raises tempo to match the rising energy even when you did not ask it to.
How to spot it: Look at your section labels. If they imply rising intensity, tempo will follow.
3. Genre mixed with implied higher-BPM genre
“Chill house with breakbeat elements” — breakbeat lives at 140-160 BPM. The model averages, and the average drifts toward the faster genre as the song develops.
How to spot it: Drop the secondary genre and re-generate. If tempo stabilizes, the genre mix was pulling it.
4. Extend / continue operation re-anchored tempo
Using Suno’s Extend feature on a song imports the previous segment’s “feel” but the new segment is independently generated. It can land 4-8 BPM off, and the seam is audible.
How to spot it: Listen at the extend point. If you hear a slight tempo step, the extend re-anchored.
5. Vocal style implies a different tempo
“R&B vocals” at “140 BPM trap” pull in opposite directions. R&B phrasing is slower; the model often slows the instrumental to fit the vocal feel.
How to spot it: Generate instrumental-only at the same prompt. If instrumental stays at tempo and the vocal version drifts, the vocal was the source.
6. Long song amplifies drift
Songs > 3 minutes have more room to drift. A 30-second clip might hold tempo within 2 BPM; a 4-minute track can drift 10+ BPM.
How to spot it: Trim the prompt to 90 seconds. If the short version holds tempo, length amplification is the cause.
7. Prompt mentions specific reference artists with varied tempos
“In the style of Daft Punk” — Daft Punk songs span 105-130 BPM. The model wanders within that range.
How to spot it: Replace the artist reference with explicit BPM and a specific subgenre.
Before you start
- Open the generated file in a DAW (Reaper, Ableton, Logic) with tempo detection.
- Note the BPM at 0:30, 1:30, and end-of-song. Drift pattern matters.
- Decide your tolerance — ±3 BPM is fine for a chill track; ±0.5 BPM is required for sync-to-video work.
Information to collect
- Exact prompt and style description used.
- Generated file BPM curve (DAW tempo analysis).
- Song length in seconds.
- Whether Extend was used and at which timestamp.
- Section labels (verse / chorus / bridge / drop) and the energy adjectives you used.
- Vocal style description if any.
Step-by-step fix
Ordered from prompt-only fixes to post-processing rescue.
Step 1: Strip energy-escalation adjectives
Re-prompt without rising-energy language:
BEFORE: chill house, 120 BPM, building to euphoric drop, then
massive chorus, then breakdown then climax
AFTER: steady chill house at 120 BPM throughout. Same energy
from start to finish. No big drops, no climaxes.The model will hold tempo when energy is flat. Energy and tempo are coupled.
Step 2: Pin tempo at multiple points in the prompt
Repeat the BPM number across section descriptions:
[Verse] 120 BPM, four-on-the-floor kick
[Chorus] 120 BPM, same kick pattern, vocals layer on top
[Bridge] 120 BPM, sparse, no drum drops
[Outro] 120 BPM, fadeThe model treats each repetition as reinforcement. See also Suno BPM off target for the more general BPM mismatch problem.
Step 3: Use a single, consistent genre tag
Drop genre mixes for the first pass:
BEFORE: chill house with breakbeat and dnb fills
AFTER: chill house, deep house, minimalAll three subgenres in the “after” line live around 120 BPM. Once tempo is stable, you can re-add breakbeat elements at lower weight.
Step 4: Generate at the target length, not longer
If you need 2 minutes, prompt for 2 minutes. Generating 4 minutes and trimming gives more drift room mid-song.
Length: 2 minutesIf your tool offers length presets, pick the one closest to your need.
Step 5: Bypass Extend by regenerating with longer base
If you need a 4-minute song, generate the full thing in one pass at the longest available length rather than extending. Extend introduces a tempo step at the seam.
Step 6: Post-process: time-stretch to a stable grid in DAW
If the model refuses to hold tempo:
- Import to your DAW.
- Detect tempo per bar (Ableton: Warp; Logic: Flex Time; Reaper: stretch markers).
- Quantize each bar to 120 BPM.
- Export.
Modern time-stretch on a 2-3 BPM drift is inaudible. On a 10+ BPM drift it audibly artifacts on the kick — re-generate instead of fixing.
Step 7: For sync-critical work, generate instrumental and overdub vocals
If you need exact BPM for a video edit, generate the instrumental only (often more tempo-stable), then re-generate or re-record vocals separately at exact tempo. Compositing two stable tracks beats fixing one drifting one.
Verify
- Re-analyze BPM curve after re-generation. Drift across the full song should be within ±2 BPM.
- The downbeat at 0:00, 1:00, 2:00 should land on whole-second multiples if you targeted 120 BPM.
- Loop a 4-bar section against the full track. If they stay in phase, tempo is stable enough.
Long-term prevention
- Use flat-energy prompts when tempo stability matters. Reserve “build / drop / climax” language for tracks where drift is acceptable.
- Repeat BPM in every section label, not just the global prompt.
- Avoid genre mixing in the first pass. Add layering / fills in post.
- Keep song length to the minimum you need.
- Never use Extend for sync-critical work; always full-generate.
- Maintain a per-style “BPM stability” cheat sheet — chill house holds well, drum-and-bass with breakbeat fills does not.
Common pitfalls
- Trusting the BPM number you wrote in the prompt without ever measuring the output.
- Writing “build to a climax” and being surprised that the climax is faster.
- Using Extend to make a 1-minute clip into 3 minutes — guarantees a seam.
- Mixing genres at different native tempos without flagging the dominant one.
- Quantizing a 10-BPM-drift track in DAW and shipping it — kicks sound like stretched rubber.
- Not measuring tempo at all and trusting your ear, which adapts to slow drift over a few minutes.
FAQ
Q: Does Suno have an actual BPM lock setting?
Suno’s prompt accepts BPM and respects it loosely; there is no hard lock. Udio is similar. Some specialized tools (AIVA, Loudly) offer stricter tempo control if you need it.
Q: Why does the kick stay steady but the music feels wobbly?
Models can keep a four-on-the-floor kick visually-on-grid while pushing hats, snares, and melody slightly off. The “feel” drifts even when the kick does not. Look at the entire arrangement, not just the kick.
Q: Can I use stems to fix drift after the fact?
Yes if the stems are quantized independently — re-grid each stem to a metronome track, then re-mix. Suno’s stem export (when available) makes this possible. Without stems, fixing drift is hard.
Q: Is this only a Suno issue?
No. Udio, AIVA, MusicGen, and Stable Audio all exhibit some tempo drift. Suno is most-reported because it has the largest user base. The mitigations here apply across tools.
Related
- Suno BPM off target
- Suno song too short
- Suno lyrics out of sync with melody
- Suno stem export missing
Tags: #Troubleshooting #ai-music #Suno #tempo #bpm