Overlap

 

4 is a balanced value in terms of speed/SDR according to measurements (since the beta patch #3 or later used above, overlap 16 is now the slowest (not overlap 2 anymore) and overlap 4 has a bigger SDR than overlap 2 now.
Some people still prefer using overlap 8, while for others it’s already an overkill.
There’s very little SDR improvement for overlap 32, and for 50 there’s even a decrease to the level of overlap 4, and 999 was giving inferior results to overlap 16.

Compared to overlap 2, for 8 “I noticed a bit more consistency on 8 compared to 2 (less cut parts in the spectrogram).”
Instrumentals with overlap higher than 2 can get gradually muddier.

So the highest SDR gives overlap 32, but for drastic separation time increase vs 16.
Calculations above were based on evaluations conducted on multisong dataset on MVSEP. Search for e.g. overlap 32 and overlap 16 below, and you will see the results to compare:

https://mvsep.com/quality_checker/multisong_leaderboard?algo_name_filter=kim

“overlap=1 means that the chunk will not overlap at all, so no crossfades are possible between them to alleviate the click at edges.”
The setting in GUI overrides the one in the model's yaml.

 

Check out also MVSep/ZFTurbo analysis on overlap here.

 

Refer to UVR Roformer beta patch section for more detailed information