This works well for me and can probably be tweaked as needed for others.
To start:
The standard way to tag Artist is to have an Artist field for all music files. The standard way to tag Album Artist is to have a value like 'Soundtrack', 'Varied', etc. for compilation albums only. Album artist should be blank for non-compilation albums.
With files tagged properly they work with JRiver's 'Album Artist (auto)' field as well as other software like foobar. I have always liked to combine the two fields into a field call 'Artists'. It's my preferred way to browse my collection, but has the downside of not supporting Artist images and also not being compatible with other apps (I use foobar mobile on my DAP because it runs android 5 and JRiver is not available).
Now that JRiver has added Image support for the 'Composer" field I have started using it instead of 'Artists'. To get Artist images to show up for the Composer field I simply copy the Artist cover art folder and rename it Composer.
After years of delaying I recently got around to adding even more fields into my combined artist list. I am now also adding Featured Artist, Covered Artist, And Remixing Artist.
The simple explanation of how I do it is this:
I made the following user fields:
Artist Covered
Artist Featured
Artist Remixing
Artist Combined
I combine Artist, Album Artist, Artist Covered, Artist Featured, Artist Remixing into one field called Artist Combined.
Artist Combined is a calculated field and this is the expression:
listbuild(1,;,[Artist Covered],[Artist Featured],[Artist Remixing],[Album Artist],[Artist])&datatype=[list]
I then copy Artist Combined into the Composer field.
Here's the fancier stuff:
I auto populate the Artist Covered, Artist Featured, and Artist Remixing fields by parsing the song names.
In my song names i use square brackets and list the Covered Artist first, the Featured Artist second, and the Remixing Artist third.
Some Examples:
Gimme, Gimme, Gimme [Black Flag Cover]
Man in the Box [Alice in Chains Cover]
Simple Man [Lynyrd Skynyrd Cover]
Reflektor [Ft David Bowie]
Two Birds, One Stone (Renholdėr Mix) [Ft Wes Borland Rmx Renholdėr]
Highwayman [Ft Waylon Jennings; Willie Nelson; Kris Kristofferson]
Weak and Powerless (Tilling My Grave Mix) [Rmx Renholdėr; Wes Borland]
Smoke and Mirrors (The Beta Machine Mix) [Rmx The Beta Machine]
Judith (Renholdėr Mix) [Rmx Renholdėr]
Immigrant Song [Led Zeppelin Cover Ft Trent Reznor & Atticus Ross]
The Cover Of The Rolling Stone [Dr. Hook & The Medicine Show Cover Ft Hayes Carll]
Bring Me the Disco King (Renholdėr Mix) [Ft John Frusciante; Maynard James Keenan Rmx Renholdėr]
I use the following calculated fields to auto fill in the values:
Artist Covered
regex([Name],/#\[(.+?) Cover#/,1)&datatype=[list]
Artist Featured
regex([Name],/#(\[Ft |Cover Ft )(.+?)(\]| Rmx)#/,2)&datatype=[list]
Artist Remixing
regex([Name],/#Rmx (.+?)\]#/,1)&datatype=[list]
The reason the expressions work is because of the consistent way I use 'Ft', 'Cover', and 'Rmx'.
I have been using the Composer field like this for a couple weeks now and it has been working perfect. It's great to have my artist fields combined and the Composer images are showing up without issue on JRemote and MO 4Media.