I remastered a couple of tracks that had some audio quality issues.

The first was “A Woodsmith’s Fear” by Magnus Jansson. There was audible clicking throughout the song. Looking at the track in OpenMPT, I could see there was garbage at the start and end of most of the samples. It looks like they were imported improperly at the time the track was composed. The fix was simple: Select the garbage, hit delete, and consign it to oblivion.

The second was “Spiral Minds” by Plastik. This track has some vocoded vocals around the midpoint of the song, which were audibly distorted. Once again, I took OpenMPT to the track. This time there were no obvious issues in the recorded samples themselves; the problem must be how the track was laid out.

Upon further investigation, I discovered that when the samples were played in the song, they were duplicated over nine channels. That is: When the sample was played, it was played nine times, effectively amplifying it so much that it caused clipping.

I tried removing the surplus copies of the sample, and discovered the reason the author had done it: The vocals were almost inaudible. Apparently there was too much going on with the rest of the song, so the vocals were just drowned out, and the additional copies were an attempt to compensate.

The proper fix would have been to decrease the volume of everything else, but there doesn’t seem to be an automated way of doing that in OpenMPT. So I did a bit of a dirty hack: I rendered the music and vocals to separate tracks, then opened them in Audacity, and adjusted the volumes until they were a reasonable balance. The result: Good clear vocals audible over the music.