uses
 MMSystem;

// Play Midi

procedure TForm1.Button1Click;
const
 FileName = 'C:\YourFile.mid';
begin
 MCISendString(PChar('play ' + FileName), nil, 0, 0);
end;

// Stop Midi

procedure TForm1.Button1Click;
const
 FileName = 'C:\YourFile.mid';
begin
 MCISendString(PChar('stop ' + FileName), nil, 0, 0);
end;