usability or expression

The volume should be equalised by each single track or as a whole?

In both cases there is an usability problem.

Equalising by single track, the evolution of the volume through the album is lost.

Equalising by whole album, the listener might not ear or hear too loud when changing an album.

One might say that the persons mastering should be given an option in order to express themselves as desired.

This could be seen as an usability problem, or a matter of expression.