UMG and other labels believe that when consumers download song recordings via the internet or on a mobile phone, it constitutes a sale. However, many recording artists say that, as there are few manufacturing costs involved, the transaction is more like a license.

The move follows a lawsuit filed by Eminem's publisher FBT Productions last year and UMG could be forced to pay a sizable sum on digital formats for the two artists.

If Zombie and James are successful with ...