Peter,

now this is such a much better idea, and simpler than mine. So, expanding it a little bit, maybe what we need is simply ONE extra field. Whenever we do not like ANY of the standard fields for sorting pourposes, we can "activate" the extra fileld, type something in and have the song sorted by that. We could in theory have the extra field replace any of the standard ones by simply selecting in some way (checkboxes, list, and so on) WHAT field should be replaced by the extra one, in sorting procedures.
Now, am I making sense? What do you think?