So I have the exact same issue as everyone else here. I have a Logitech K750 wireless keyboard running Yosemite on my MBP.
I don't necissarily think this issue resides with Spotify, but instead with Logitech. If I use the media keys on my MBP I am capable of using Next/Previous even when Spotify is in the background. On the wireless keyboard only Play/Pause and the Volume buttons work. I think the issue is with the key mapping with the Logitech.
Then again, I don't know how the code is written. Maybe Spotify missed an alternative key map for the media buttons. I didn't write the code....
The logitech forum is a ghost town for this issue though. Only post I found was 5 years old.
EDIT: With further reasearch I DO believe the problem lies with Spotify. A tech for Logitech explained to me that Spotify wrote some "interesting" code for the keymap functionality for its Mac client. A quick Google search shows that it is not only Logitechs experiencing this issue. It would be great if we could get someone to look into this. It isn't critical, but it sure would be nice to get fixed.
I am running OSX 10.10.2 with Logitech K520 keyboard at latest version of OSX Spotify. Media keys are fully functional with itunes. For spotify Play/Pause is functionl, while previous track and next track do not work.
Spotify please fix this bug ASAP. This has been an oingoing problem for a long time now.
I have programmed a custom keyboard so that it does this, fakes out the computer to be an Apple. This is not the solution. The keyboard, in normal mode or in fake Apple mode, doesn't work for next or previous. They both do in fact work for iTures.
Screenshot of the working KB (ES-87) and the non working (ps2avr), but both show to be the same vender and hardware ID numbers.
Re: Next / Previous media keys don't work on 3rd Party Keyboard, Play/Pause does work. [MAC]