audio files for comparison

The same technique is used at the beginning of Fury Forest by Moby (https://modarchive.org/index.php?request=view_by_moduleid&query=40814). I have attached audio comparisons for this one as well. The effect on Amiga is once again much more percussive. IMO, OpenMPT should still have a tiny amount of ramping to avoid the clicks you hear here, but I would argue that OpenMPT's current amount of ramping in this context is too smooth.

Note that on-the-fly sample swapping needs to be enabled in compatibility settings for proper playback of this module.

Indeed, when using instrument numbers + volume slides the volume was ramped over a whole tick. This didn't happen when instead using set volume + volume slide (a combination that's not possible in the MOD format but is for example possible in XM, S3M and IT). The behaviour has now been made consistent between those two possible ways of the gating effect. While it's a small change in code, it is a big change in practice affecting potentially many modules out there. Hence I'm not quite comfortable in backporting it to older OpenMPT or libopenmpt versions (yet), and will keep the fix from r18739 in the upcoming major update (OpenMPT 1.31) only.