Play two sounds simultaneusly

The "MediaPlayer" object will not let you play two sounds at once, even if you create two instances. You will need to bring in the native windows API "mciSendString".

    [DllImport("winmm.dll")]
    static extern Int32 mciSendString(string command, StringBuilder buffer, int bufferSize, IntPtr hwndCallback);

    public Form1()
    {
        InitializeComponent();

        mciSendString(@"open C:\Users\Jono\Desktop\applause.wav type waveaudio alias applause", null, 0, IntPtr.Zero);
        mciSendString(@"play applause", null, 0, IntPtr.Zero);

        mciSendString(@"open C:\Users\Jono\Desktop\foghorn.wav type waveaudio alias foghorn", null, 0, IntPtr.Zero);
        mciSendString(@"play foghorn", null, 0, IntPtr.Zero);

    }

Reference PresentationCore and WindowsBase and try this...

var p1 = new System.Windows.Media.MediaPlayer();
p1.Open(new System.Uri(@"C:\windows\media\tada.wav"));
p1.Play();

// this sleep is here just so you can distinguish the two sounds playing simultaneously
System.Threading.Thread.Sleep(500);

var p2 = new System.Windows.Media.MediaPlayer();
p2.Open(new System.Uri(@"C:\windows\media\tada.wav"));
p2.Play();

EDIT I received a downvote probably because at first glance this looks like it will play the second sound after the first is finished. It doesn't, they are played by windows asynchronously. The sleep is there so if you test this code verbatim you can hear the sounds play together, it wouldn't be noticeable without the delay since they are the same sound.

This code demonstrates the two sounds playing on separate threads on top of each other, which is sort of pointless since the playback doesn't block anyway

new System.Threading.Thread(() => {
        var c = new System.Windows.Media.MediaPlayer();
        c.Open(new System.Uri(@"C:\windows\media\tada.wav"));
        c.Play();
    }).Start();

System.Threading.Thread.Sleep(500);

new System.Threading.Thread(() => {
        var c = new System.Windows.Media.MediaPlayer();
        c.Open(new System.Uri(@"C:\windows\media\tada.wav"));
        c.Play();
    }).Start();

http://msdn.microsoft.com/en-us/library/system.windows.media.mediaplayer.stop.aspx The class also has the control you need to stop playback