Spotify has added thumbs to its desktop radio, allowing listeners to fine tune an artist station by giving a song a "thumb up" or "thumb down."

This is the latest in what's sure to be a lot of tweaking to its radio product. Spotify has long offered a radio service on its desktop application, but the company got more serious about radio when it launched a free radio service on its iOS app - with thumbs - in June. But Internet radio is difficult to do well, and Spotify's song selection will occasionally leave a bit to be desired.

Spotify Reveals New Numbers: Over 4 Million Subscribers and 15 Million Active Users

Every thumb will help. Internet radio is a competitive space with more well funded companies and greater innovation than meets the eye. TuneIn, for example, which l ast week announced $16 million in fresh funding, got some attention over the weekend for live streaming the Outside Lands music festival from San Francisco. While TuneIn lacks the personalized features of Spotify and Pandora - it lacks thumbs, in other words -it does have an easy-to-use mobile app and a ton of content.

A couple recent cases in point show how Internet radio is making an impact. One is last week's Warner Music Group earnings report. The company's recorded music division now gets 25% of its digital revenue (not total revenue, just digital revenue) from subscription, on-demand and webcasting services such as Spotify, YouTube, and Pandora (all of which allow users to "thumb" songs). Warner didn't break out the lump of revenue by company type, but the message was clear: fractions of pennies from streaming services add up with enough volume.

Business Matters: Warner Getting Big Gains from Spotify, Pandora, YouTube and other Streaming Services

The other example was a breakdown of musician Zoe Keating's revenue over a five-month period. Now, Keating gets almost all of her recorded music revenue from purchased music - not a surprise for an independent artist. But she does make a small amount from digital performance royalties, too. As a spreadsheet she posted online shows Keating made $1,278.19 as a performer and rights owner over two quarters (almost all from Pandora).