The people behind Information is Beautiful, who create visualizations of data, made this table to illustrate how much money musicians make from various media.
Here’s the data for Spotify, a service that provides free, unlimited, on demand streaming of songs, albums and playlists in exchange for advertising interruptions.

Spotify pays Mumford & Sons $0.00029 every time I listen to any of their songs. (Their record makes $0.0016.)
According to Last.fm, a service which (for my purposes) logs my listening history, I’ve listened to Mumford & Sons 901 times as of today.

901 times, over 1 year and 7 months.
So how much money has Mumford & Sons made from my use of Spotify?

$0.26. 26 cents.
(I did buy their album, so my patronage totals out at something like $8.26.)