I saw this in a YouTube video, but felt it worthy of a C# 6.0 upgrade :-).
The Happy Birthday song in C#:

using static System.Console;
using static System.Threading.Thread;

namespace DevelopOne.HappyBirthday
{
    class Program
    {
        static void Main( string[] args )
        {
            WriteLine( "Everybody sing along!" );
            Sleep( 2000 );
            Beep( 264, 125 );
            Sleep( 250 );
            Beep( 264, 125 );
            Sleep( 125 );
            Beep( 297, 500 );
            Sleep( 125 );
            Beep( 264, 500 );
            Sleep( 125 );
            Beep( 352, 500 );
            Sleep( 125 );
            Beep( 330, 1000 );
            Sleep( 250 );
            Beep( 264, 125 );
            Sleep( 250 );
            Beep( 264, 125 );
            Sleep( 125 );
            Beep( 297, 500 );
            Sleep( 125 );
            Beep( 264, 500 );
            Sleep( 125 );
            Beep( 396, 500 );
            Sleep( 125 );
            Beep( 352, 1000 );
            Sleep( 250 );
            Beep( 264, 125 );
            Sleep( 250 );
            Beep( 264, 125 );
            Sleep( 125 );
            Beep( 2642, 500 );
            Sleep( 125 );
            Beep( 440, 500 );
            Sleep( 125 );
            Beep( 352, 250 );
            Sleep( 125 );
            Beep( 352, 125 );
            Sleep( 125 );
            Beep( 330, 500 );
            Sleep( 125 );
            Beep( 297, 1000 );
            Sleep( 250 );
            Beep( 466, 125 );
            Sleep( 250 );
            Beep( 466, 125 );
            Sleep( 125 );
            Beep( 440, 500 );
            Sleep( 125 );
            Beep( 352, 500 );
            Sleep( 125 );
            Beep( 396, 500 );
            Sleep( 125 );
            Beep( 352, 1000 );
            WriteLine( "Yeahhhhh, happy birthday!" );
            ReadLine();
        }
    }
}