Anyone else remember the bad old days of DRM-ed music? Pre-2013, when the music industry didn't trust anyone and so all digital downloads came encumbered in Digital Rights Management encryption? Yes, it was a dark time and anyone in the know avoided such DRM music like the plague and bought (or scraped/converted) from other sources. However, just in case there are users here with purchased DRM-ed music from the first year or two of Windows Phone's existence, note the Microsoft advisory, quoted below. Best grab the free MP3 versions of any purchased tracks while you still can, since the old (WMA format) music won't work under the Windows 10 Mobile Anniversary Update, on phone or PC. 

And yes, in all this hassle and complexity there's a lesson. Which, thankfully, the industry worked out fairly quickly. Sell digital music DRM-free - since pirates will just carry on pirating anyway and honest users shouldn't be annoyed at every turn. Today, in 2016, an awful lot of people can download music for free by various means, but - thanks to affordable mobile data - the majority have switched to 'streaming' services, offering every track on the planet (well, almost) in exchange for a simple small monthly fee. Hey, who knew that it would all work out OK after all?

From the Microsoft advisory:

Did you buy songs from Zune Marketplace before 2012? Unless you take action, certain songs—specifically, downloads encoded using WMA DRM—will stop playing after March 12th, 2017.

Since April 2011, Zune and other Microsoft music services—including Windows Store and the current Groove service—have sold music encoded only in the MP3 format, which has no DRM.

• After installing the Windows 10 Anniversary Update, any songs you downloaded as WMA DRM files will no longer play. WMDRM rights management was introduced a long time ago, and it’s been replaced by PlayReady and other technologies. 
  However, as long as the songs are still part of the Groove catalog, you’ll be able to stream those songs in the Groove app or at the Groove website (https://music.microsoft.com), or download them as MP3 for free.
• On versions of Windows older than the Windows 10 Anniversary Update (such as Windows 7, Windows 8, etc.), songs encoded with WMA DRM will continue to play as long as your PC has a license and you’re using a music app made by Microsoft, such as the Zune software or Windows Media Player. 
  We recommend, however, that you download your past purchases as MP3s for free while it’s still possible, because Microsoft will no longer supply fresh licenses for WMA DRM files (if, for instance, you reinstall Windows) after March 12th, 2017.
• On Windows Phone 7, Window Phone 8, and Zune devices, songs will continue to play until something happens to invalidate their licenses (file corruption, system update, etc.). You can relicense purchases by playing each individual song before March 12th 2017, but instead we recommend downloading the MP3 version on your PC as soon as possible.

What do I need to do?

On a computer, download your past purchases as MP3 for free. Note: This works only for songs that are still part of the Groove Music catalog. Some songs have been removed at the request of their copyright holders.

In the Groove app on Windows 10:

1. Sign in to Groove app using the same Microsoft account you used to buy the music from Zune Marketplace.
2. Select Songs > Filter > Purchased.
3. Select one song, then click-right and choose Select all.
4. Right-click again and select Download.

On versions of Windows 8.1 or earlier, and on others operating systems:

1. Sign in at music.microsoft.com using the same Microsoft account you used to buy the music from Zune Marketplace.
2. Select Collection > Songs and filter for Purchased music.
3. Mouse over a song you want to download and select More (“…”), then Download. Repeat for as many songs you want to download.
   Note On the web, you can download each song only once.

What about songs I bought as MP3s?

Any MP3s, whenever and wherever they were purchased, are not affected. MP3 songs will continue to play normally using your current apps and devices.

Amusingly, the piece finishes with one of the classic ways of getting DRMed content into DRM-free form - go via a physical audio CD(!):

What if some of the songs aren't available as MP3s?

Some songs might play in the Zune software even though they’re not in the Groove music catalog. To preserve those songs, burn them to an audio CD.

1. In the Zune software, right-click the songs you want and select Add to burn list.
2. Insert a blank CD.
3. Select the disc icon, then Start burn.

So there we go. I doubt that many people here will be affected by this, but it's good to be aware of. DRM-encumbered music was always going to fail in the Napster/Torrent/YouTube age, and now that we have a good model in all the £10-a-month streaming services there's no reason for DRM-ed audio to exist anymore.