Quote:
Why in some songs there is no any difference if coupling is at 0 or at 100% ?
Ok... a little difference , as little as possible

I'm starting to think, the better the multiband is configured such that all bands on average have the same level, the less effect coupling will have. That makes sense: If all bands are NOT on the same average level, the sound will change when the volume drops, which is also a type of spectral imbalance.
I tried it on Bojcha's R-Style preset and heard nearly no difference, however with PhantomFM's 80s Style the difference is a lot bigger.
In the case of the song where I heard spectral imbalances (Spider Murply Gang - Skandal im Sperrbezirk) Jeroens preset really improves if I set to to 40%, in Bojcha's preset I hear nothing - even very little if I set it to 100%.
I probably need to add 'median display' in the Multiband section again (was present until version 6.32), which shows the median position of each band over a long period; that helps in making presets sound more stable. (Just for clarity: You CAN make it sound stable without actually changing the sound except for moments where there are problems).
Band coupling is still a good thing (not all tracks are equal on the input), but I do need to think of something at the extremes (first and last band).