[madisp]

afaik Spotify does none of those ways. They take the total amount of money earned per time period and divide it to artists based on the total_artist_playcount / total_playcount in that time period, after taking their own percentage cut. It's closest to Way 1, with the difference that you can listen to whatever - if Taylor Swift is the most popular artist right now and gets, say, 1% of all plays then 1% of your subscription will go to Swift.