What's old is new again at Last.fm: On-demand listening is returning to the music recommendation service thanks to a newly announced partnership with Spotify.

Last.fm killed a previous on-demand listening feature back in 2010, though radio-style listening remained available (which itself was recently buoyed by YouTube) along with the service's signature "scrobbling," which tracks your tunage to spit out tailored music recommendations.

Spotify's desktop player has offered Last.fm integration (via an optional app) for a while now, but the new deal bakes Spotify's songs into the Last.fm interface, albeit in beta form.

If you're browsing Last.fm and have a Spotify account, clicking on the new Play icon next to a song, artist or album that's available in Spotify's 20 million song-strong library will launch Spotify in either desktop or web player form (depending on whether or not you have the desktop player installed).

Theoretically, the feature shouldn't even yank you out of Last.fm's arms; a set of Spotify playbar controls appear at the bottom of the Last.fm screen so you can control the on-demand songs without leaving Last.fm proper.

I had some troubles getting these to work beyond launching the initial song, however--I had to shift to the Spotify interface to skip through songs in an album, and sometimes clicking the Play icon next to a Last.fm track generated a "Link not found" error in the Spotify desktop player. Additionally, Chrome flat-out refused to launch Spotify or the playbar controls whatsoever, though Firefox and Internet Explorer at least loaded the songs. (The playbar controls were still hit-and-miss.)

But hey, that's what betas are for, right? It's just good to see Last.fm slinging songs on-demand again. Hopefully the kinks get worked out in short order.