How to play a wav-File in Delphi?

With the function sndPlaySound from the WIN32-API (Unit MMSystem):

sndPlaySound('C:\Windows\Media\Tada.wav', SND_ASYNC);

People keep quoting sndPlaySound, but this is quite obsolete, and it is available in Delphi for backward compatibility only. So, stop using it!

---

That being said, use:

procedure PlaySoundFile(FileName: string);
begin
 if FileExists(FileName)
 then PlaySound(pchar(FileName), 0, SND_ASYNC or SND_FILENAME);  
  
 { Flags are:
    SND_SYNC  =0 = Start playing, and wait for the sound to finish
    SND_ASYNC =1 = Start playing, and don't wait to return
    SND_LOOP  =8 = Keep looping the sound until another sound is played  }
end;

---

To play a predefined Windows sound, use this:

procedure PlayWinSound(SystemSoundName: string);
begin
 Winapi.MMSystem.PlaySound(PChar(SystemSoundName), 0, SND_ASYNC);
end;


For SystemSoundName use one of the constants below:

  SystemEXCLAMATION        - Note)
  SystemHAND               - Critical Stop)
  SystemQUESTION           - Question)
  SystemSTART              - Windows-Start)
  SystemEXIT               - Windows-Shutdown)
  SystemASTERIX            - Star)
  RESTOREUP                - Enlarge)
  RESTOREDOWN              - Shrink)
  MENUCOMMAND              - Menu)
  MENUPOPUP                - Pop-Up)
  MAXIMIZE                 - Maximize)
  MINIMIZE                 - Minimize)
  MAILBEEP                 - New Mail)
  OPEN                     - Open Application)
  CLOSE                    - Close Application)
  APPGPFAULT               - Program Error)
  Asterisk                 - played when a popup alert is displayed, like a warning message.
  Calendar Reminder        - played when a Calendar event is taking place.
  Critical Battery Alarm   - played when your battery reaches its critical level.
  Critical Stop            - played when a fatal error occurs.
  Default Beep             - played for multiple reasons, depending on what you do. For example, it will play if you try to select a parent window before closing the active one.
  Desktop Mail Notif       - played when you receive a message in your desktop email client.
  Device Connect           - played when you connect a device to your computer. For example, when you insert a memory stick.
  Device Disconnect        - played when you disconnect a device from your computer.
  Device Connect Failed    - played when something happened with the device that you were trying to connect.
  Exclamation              - played when you try to do something that is not supported by Windows.
  Instant Message Notif    - played when you receive an instant message.
  Low Battery Alarm        - played when the battery is running Low.
  Message Nudge            - played when you receive a BUZZ in an instant message.
  New Fax Notification     - played when you receive a fax via your fax-modem.
  New Mail Notification    - played when you receive an email message.
  New Text Message Notif   - played when you receive a text message.
  NFP Completion           - played when the transfer of data via NFC between your Windows device and another device is completed.
  NFP Connection           - played when your Windows device is connecting to another device via NFC.
  Notification             - played when a default notification from a program or app is displayed.
  System Notification      - played when a system notification is displayed.

All available constants are defined in the registry under the path HKEY_CURRENT_USER -> AppEvents -> Schemes -> Apps -> .Default.

Here's the fastest way:

uses MMSystem;

procedure TForm1.Button1Click(Sender: TObject);
begin
  sndPlaySound('C:\Windows\Media\Tada.wav',
    SND_NODEFAULT Or SND_ASYNC Or SND_LOOP);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  sndPlaySound(nil, 0); // Stops the sound
end;