Hi, what would be the “artist” name if a song is instrumental? I couldn’t find it in help section.
Hi josph, it doesn’t really matter if there’s vocals or not, it just means you wouldn’t assign any kind of ‘[artist] does vocals on [recording]’ relationship, because that obviously doesn’t exist.
For the track artist, just put the album artist as usual, or use whoever’s credited in the credits/ on the back of the release 
edit: let us know if it’s still a bit unclear
To add to @aerozol’s answer, the relevant guideline is doc/style/artist credits.
On a separate note, as it says in the Discourse guidelines:
I moved this into a new topic.