Автор: http://www.swissdelphicenter.ch

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;