might be a bit self-explanatory, but if an artist—who isn’t/wasn’t a member of the band—is credited as doing vocals or instruments on a track, should they be credited with the “Guest” attribute even when it’s not mentioned in the booklet?
a hypothetical example, in a booklet you’ve got a list of say, band members X on guitar, Y on drums, and Z on bass, but artist G is credited as doing guitars on track 5. would artist G be credited as “Guest guitars” then?
moreover, I’ve seen a couple examples where some guests aren’t credited as “Guest” in a booklet, but others are. continuing the example above, artist S is credited as “Guest Synths” on track 3. should both G and S be credited as “Guest”, or just artist S?
one point, just for completeness’s sake, this probably shouldn’t apply when a band member left while recording an album. for example, artist L did guitars on tracks 2, 7, & 8 with X. they should probably not be credited as “Guest”, by any stretch.