Step 1 - go to the relationship editor and add Bären Gässlin as Artist \ Performer or Artist \ Orchestra to all the recordings. Quickest way to do this is tick all of them, then use “Batch add relationship to recordings”
Step 2 - grab loujine’s “Replace recording artists from a Release page” userscript. Go back to the main releases page and it will now let you copy that performer\orchestra relationship to the Recording artist on all the tracks.
If you don’t yet know what Userscripts are, that is for a separate reply. Making use of userscripts adds all kinds of powerful extra abilities to the site that can safe a ton of editing time.