Various – 音楽長屋

The label for side A lists 6 tracks. The meaning of 付録 is "appendix", like bonus track. So it is essentially track 7 of side A.

The meaning of その他音痴多数 is "Other people who are not good at singing". So it is not technically an artist name, more like "guest musicians". But Discogs needs an artist, so it's "その他音痴多数."