Just a short time ago, the mobile platform ecosystem story was easily explained: You could only get the best experience if you stuck within the confines of what Apple, Google or Microsoft offered you on the respective platforms. But things are changing. And you can increasingly mix and match your ecosystem choices at will, using the devices and services you prefer.

What triggered this was two software releases today that don't seem, on the surface, to impact readers of this site at all: Google Music for iOS (iPhone, iPad, iPod touch) and Amazon Instant Video for the Sony PlayStation 4. But these are just the latest in an increasingly long line of cross-platform releases that make it easier than ever for us to choose how we wish to mix and match devices and services.

Some of this stuff has been going on for a long time, of course. Microsoft has long supplied a version of Microsoft Office for the Mac, for example, and iTunes and the iPod didn't take off until Apple ported the digital media software to Windows, which was at the time the single dominant personal computing platform.

Today, we juggle PCs with an increasingly complex web of smart phones, tablets, video game consoles and other devices. We have mature digital media ecosystems from Amazon, Apple, Google and Microsoft from which to choose. We're seeing Office makes inroads on the web, the iPhone and Android handsets, and next year we can expect touch-first versions of the software for Windows and the iPad.

With the wider world turning to competing mobile platforms like Android and, to a much lesser extent, iOS, Microsoft has been at the forefront of what I think of as the modern cross-platform age. I'll be writing more about specific Microsoft apps you can find on Android and iOS in the near future, but here let's just look at a single example, which is interesting because it's sort of unexpected: Xbox Music.

Xbox Music launched last year as the successor to Zune Music. It inherited much of what made Zune Music great—like Zune Music Pass—dumped some legacy features that still rankle dedicated Zune fans—like podcasts, song ratings and auto playlists—but added some pretty amazing—and still evolving cloud-based functionality. Those who are still more comfortable with the old-fashioned way to doing things (where your PC sits at the center and you sync music to devices from there) find Xbox Music a bit confounding. But I really like and recommend the service, and it's been interesting watching it get better and better throughout 2013.

Xbox Music began this year with basic native clients on Windows 8 (and RT), Windows Phone 8, and Xbox 360. But throughout the year, each has been improved somewhat, and in the case of Windows 8.x, quite significantly. A web client was added, and also improved over time. And then Microsoft shipped native Xbox Music mobile apps for Android and iOS. Xbox Music ships on the Xbox One next week, too.

This more agnostic approach—Zune was specific only to Microsoft's platforms and the web—makes it much easier for users to choose the devices they prefer and match them with the services—in this case, Xbox Music—that they prefer, in ways that were not previously possible. The Android and iOS apps are still pretty basic—they lack song downloading and offline usage, for now, though that's coming—but steadily improving. So Microsoft no longer needs to lose across the board when someone choose an iPhone or Nexus 5, or whatever: Those users can still access their Xbox Music Pass content. And their Outlook.com and Office 365 email. And their SkyDrive and Office documents. And so on.

Microsoft isn't alone in this approach. Amazon makes its Amazon MP3, Audible, Instant Video, and Kindle services available (if somewhat haphazardly) across multiple platforms. And Google has a growing history of providing most of its services on iOS. Only Apple ignores the rest of the world, and one wonders how much longer that can last given the dominance of Android on the devices side.

My only wish is that this behavior was more consistent. Amazon doesn't provide its Amazon MP3 or Instant Video services on Windows 8.x or Windows Phone, for example, and it's Kindle and Audible software is decidedly less powerful on Windows platforms than elsewhere. I'd love to be able to access my purchased iTunes content from my Surface 2 or Xbox One as well.

I can dream. But things are much better today than they were before, helping to eliminate the unnatural barriers that platform makers erect to lock in their users. I'd rather see these companies—Amazon, Apple, Google and Microsoft—try to poach users of other platforms by making their apps and services more broadly available. That's a much better approach to holding your own users captive.