Mixing/mastering
If you already did your best in separating your track, tried out ensembles or manual weighting, also read tips to enhance separation, but if it lacks original track clarity, you can use:
- Demudder added in the beta Roformer patch #14 in UVR (if it won’t increase vocal residues too much; won’t work with even small chuk_size in AMD/Intel 4GB VRAM GPUs with Roformers)
- AI Mastering services (mainly for instrumentals)
- For improving vocals' clarity, you could even “train a RVC model out of clean [artists] audio clips and then inference this audio with the model you made. It takes some time, but the results are worth it” John UVR (examples). Workflow explained later below.
- becruily/bs-roformer-delimit | Colab - fixes ducking in some songs
“if used as preprocessor before separation”
- Older Aufr33’s method - expander template for Reaper 7.05 (DL) fixing ducking in instrumentals (explained later below)
- Read Make your own remaster (more below)
Inherited flaws of instrumentals from AI separation models
Lots of audio engineers recommend leaving space for vocals in production. The result is, lots of instrumentals, no matter how good the model is, might have a hole in the midrange.
Sometimes even adding vocals to the mixture makes psychoacoustic effect making an impression that the instrumental sounds fuller. Similarly to the fact that adding artificial noise can increase fullness metrics of models.
On headphones, or by sticking one of your smartphone speakers to your ear, you might identify the constant buzzing of models easier, while even on nearfield monitors it might just make an impression that the model is fuller, and the noise won’t be noticeable, so it's deceiving.There might be always a case when someone will notice such issue during normal listening.
Also, current models have troubles with distinguishing noise of the original mixture as background of instrumentals with vocals. Buzzing pop-ins are sometimes remnants of constant noise in the mixture, sometimes louder, sometimes quieter - in places when vocals appear and disappear.
Some model results will be muddy, or also too noisy, even while using the best models or ensembles.
Also, your separation should be not destructive for any of the instruments in the song, e.g. in order to be able to be picked by a specialised single instrument model to mix it further if you wish, or just for a sake of accuracy.
So now the "perfect separation" means usually a compromise between fullness and bleedless, and sometimes you can't have both with just one model, and sounding perfect on every sound system no matter how it is sensitive in showing mentioned artefacts of separation or how much fullness you need to sound good on your system.
Hence the tolerance of certain aspects of different models might vastly differ between different people. If you already have a well-sounding separation, proceed further.
Mixing track from scratch using various AIs/models
Now if you're not afraid of mixing, and e.g. if you have clear instrumental already or whole track to remaster, then you can use the following for such a task:
- very quiet mixture (original file; so instrumental mixed vocals - if you remaster whole OG song)
- stems from demucs_ft or BS-Roformer SW (both MDX23 Colab or Ensemble of various models on MVSEP can be even better than Demucs, and vs SW esp. for bass - check out 4 stems section) mixed with also:
- drumsep MDX23C free model result (but you can also test out stems from the old drumsep and LarsNet [although they have worse SDR], or newer MVSEP drumsep models)
- GSEP result for piano or guitars (MVSEP models can be handy too, now the SW model for those stems are much better, and previously the only downloadable decent guitar model released becruily, and demucs_6s is mediocre, now we have SW)
- for bass both GSEP and Demucs ft/MDX23 aligned and mixed together (or simply from MVSEP ensemble or MDX23 Colab) or see bass models for more recent list incl. the SW
- "other" stem could be paired like above too (but drums remained only from e.g. Demucs_ft - they were cleaner than GSEP and good enough)
- Actually in one of those guitars weren't recognized in guitar stem, but were in other stem, so I mixed that all together (it wasn't busy mix)
- If it's not instrumental, probably mixing more than one vocal model might do the job, check various vocal ensembles (but it’s essentially what MDX23 and ensembles on MVSEP do, but the latter with private models, it’s not exactly the same - you can add different effects for every of such tracks, having fuller sound and change their volume manually).
The all above gave me an opportunity for a very clean mix and instruments using various plugins while setting correct volume proportions vs mastering just instrumental separation result or plain 3 stems from Demucs.
For example, demucs_ft or other single or incorporated drums model provides much higher quality of drums than the old Demus drumsep during mixing, so in such case you won’t use its stems on its own, but you will use drumsep more to overdub the specific parts of instruments more (e.g. snares - that’s the most useful part of using drumsep as normally it’s easy to bury snare in a busy mix when hi hats kick in overly in a heavily processed instrumental stem or drums stem - not you won’t have to push drums stems from demucs_ft or MDX23 so drastically).
Sam Hocking’s method for enhancing separated instrumentals from a mixture (song containing instrumental and vocals):
“I think looking at spectrally significant things like snares can work. We can already do it manually by isolating the transient audio/snare pattern as MIDI and then triggering a sample from the track itself to reinforce, but it's time-consuming and requires a lot of sound engineering to make it sound invisible.”
You can probably use Cableguys Snapback plugin for that, or maybe UVI Drum replacer.
Sam’s method will work the best in songs with samples instead of live recordings (if the same sounds repeat across the whole beat). More of those plugins.
PS. In the late 2025 we received an info about Apple Music rejecting Atmos mixes of some legacy music made with separation models (ensembles, and then probably some for 4-6 stems), even though the mixes sounded good, and were accepted by labels and artists. Also, we know that these separation methods worked fine in the past, at least for some other engineers. We suspect that they might use automated tools catching specific artefacts usually seen in separation models on spectrograms of extracted channels from the whole Atmos mix.
“I don't think there's a need of really advanced and expensive method to detect source separated stems, most of the time, just looking at the background noise is enough to tell, original stem vs separated one [click]
+ kind of "aliasing" artifacts and/or dither residues popping here and there...
There are lots of patterns than can make separated audio stems identifiable, I don't think it's hard to develop a model to spot them with quite good accuracy (even if not really audible to human ears)” - jarredou
To sum up:
Tips to enhance separation
Demudder in UVR/x-minus
(increases vocal residues)
AI mastering services