@Turbine about the music update on 15.3 and how we can help you to fix this
As it slowly turns out the new music system wasn't ready - as many suggested on the forums already.
The overall conclusion is that it's not as bad as the last attempt, but there are really a lot of quirks and problems - it's quite detrimental on some aspects of large music arrangements. Also there are those new strange issues with the positioning (run around someone playing a horn - it's a nice sound effect, but something is messed up in the sound system now)
This update is NOT an improvement, at best we can adjust to this and continue, but the overall quality goes down. Small bands that play without lutes will be able to adopt by removing some of the too loud drum sounds in their abc files, but the huge arrangements are a struggle.
I noticed by looking at the recordings that you were not following any objective method to adjust the volumes of the tones (neither normalizing or adjusting by some perception weighted system) - I guess it was all done manually by ear. This is not the way this could have turned out to be an improvement.
A lot of tones (bagpipes, some flute) have clicking sounds in the end because they are not properly faded out ( any rapid change of a slope in the sample will result in a perceived plopp ... its because edges have a lot of high frequency components ).
I'd really like a suggestion of how we should help you improving this - I could generate a huge table with volume adjustments that would result in an equalized volume on the instruments - but would you really take that into account? It would mean a lot of work to adjust basically every tone again. Are you willing to put in that developer time?
Bruzo, Dwarrowdelf Minstrel ~ "A Rock & a Hard Place"