It would be useful to have a few custom tags and/or the ability to remap some of the existing ones.

For instance, I don't have a "soloist" field but I do have a "performer" one
and it would be nice being able to remap my "performer" (multivalue) to "soloist(s)"
without having to add the "soloist" field to thousands tracks.

If it's a problem to remap to an already defined one, we could maybe have a "Custom 1",
Custom 2" and "Custom 3" fields where to remap some of our fancy info.

It would also be useful to know in detail how the remapping already in place works.

For instance, I don't have a "year" field, I have a "date" instead, but my "date" info
show up in the "year" field.

And also: how does the "bits" field work?
And the "compilation" one?
And the "contributing artist"?