iTunes has changed the game for artists music bands across the world.
Companies like TuneCore have arrangements with online digital music retailers like iTunes, Amazon MP3, Napster, etc. they can put your music in these online stores. The artist /band makes money from the digital sales and TuneCore won’t ask you for a commission.
TuneCore charges an up front fee to process recordings and upload them to music stores like iTunes – which won’t deal with individual artists. The band retains all rights to its music and keeps all the revenue past what the stores keep.
The barriers to entry are low — TuneCore charges around $10 for a single, $40 for an album, pretty much in line with its main competitor, ReverbNation — so anyone can record just about anything and offer it to the masses on a whim. And if they happen to catch a viral wave, they can end up making a decent living. link.
The following document mentions the various ways by which musicians and bands can make money by selling songs on iTunes, Nokia music store and other places through TuneCore.