Currently looking into how I can go about playing two mp3 or aac format files at the same time in Windows Phone 8.
At the moment I am using the XNA SoundEffect class but that only allows WAV files which is not ideal for transferring over a network.
While researching I ran into SharpDX but that appears to mainly be catered to .WAV or playing one file at a time.
I also discovered this question: play two sounds simultaneously in Windows 8 Metro App (C#/XAML) Multiple media elements are possible in Windows 8 but I'm not sure if they are in Windows Phone (this question seems to disagree)
Any ideas would be greatly appreciated.
UPDATE: It can't be done through MediaElement as I thought http://msdn.microsoft.com/en-us/library/windowsphone/design/hh202883(v=vs.105).aspx
You could try to do it through MediaFoundation.MediaEngine (see "Supported Microsoft Media Foundation APIs for Windows Phone 8" for guidelines on how to initialize it correctly on WP8). In SharpDX there is a Win8 samples MediaPlayerApp that could be used as a starting point to play only audio (remove all the d3d part and apply guidelines for WP8). There is also a usage of it in MonoGame MediaPlayer class.
Concerning playing multiple WAV with SharpDX at the same time, it is perfectly possible with XAudio2, and SharpDX doesn't have any limitation concerning XAudio2.
There is only a huge concern about the WP8 CLR Garbarge collector that seems to block all native threads when it is collecting, including native audio threads like XAudio2, and that could cause audio stuttering. There is nothing we can do about this, as this is an issue with the OS and the scheduling of threads with .NET.
I have also some doubt about the ability of WP8 to decode two MP3 in realtime... Let us know if you have some results.