The point of separate variables is to make them easy to use in scripts. 

I have an enhancement which I will upload soon which recreates the string used on the web site (see http://musicbrainz.org/relationship/a3005666-a872-32c3-ad06-98af558e99b0).

However, happy to use e.g. ~performance_live, ~performance_medley etc. I will make this change at  the same time.

Just trying to work out whether it is possible to work out the original performance artists from the list of recordings associated with the work i.e. look in the list of performances for those which are NOT covers or medleys then use the artist on those as the original artist (i.e. TOPE in id3). 

The problem is that I think that many recordings are actually cover versions but not shown as such which would make using this algorithm somewhat hit and miss.

For example for http://musicbrainz.org/work/f5a12d42-00a1-3bc2-8ed1-df2506ea3db2, we have (non-cover non-live) recordings by Bob Dylan, by Joan Baez, by Joan Baez feat. Bob Dylan, by Bob Dylan & Joan Baez, etc. I am very hesitant to use any form of statistical basis for weeding out the mistakes. 

But as a counter-example, for http://musicbrainz.org/work/8a9cc43c-2958-36a1-b9e9-0afd8a346285 we can be pretty sure using this algorithm that the original artist was The Beatles.

Choices then are:

1. Hit or blank - only set the original artist if all non-cover recordings have the same artist(s), leave it unset if unsure. (99.9% accurate when set.)

2. If there are two or more artists in non-cover recordings, then eliminate any recordings which have unique artists in the hope that the remaining recordings would all have the same artist(s).

3. Look for a common artist in the recording artists i.e. in the Bob Dylan example above, then Joan Baez & Bob Dylan would still indicate Bob Dylan. Or combine 2 and 3 in the hope that this would work.

4. Do nothing as we cannot be certain and we cannot be consistent.

On the whole I am leaning to 4.

Any comments on this welcomed.