Radio io has a specialty section. They have a all grateful dead station. This is the only internet radio station I can think of that is one artist only. Except for the Sirius internet dead channel. Not sure how io can do this. Must have some special contract with the band rights holders.
AOL Radio does have alot of single artist stations. Metallica , Pearl Jam , Dave Matthews , Korn , the boss aka Bruce Springsteen. There is also Green Day , Smashing Pumpkins , Radiohead , Faith Hill and Tim McGraw and Keith Urban. But what there is more B.I.G. , Slayer , Madonna , Michael Jackson Janet Jackson Luther Vandross and R Kelly. So to prove that Sirius has way too many single artist channels is a understatement to a extant , but they have more channels then Sirius XM.