[KaktoR]

You mean stop or pause?

To stop it call
BASS_Free;

To pause it create a button with a OnClick call and then something like this

procedure MusicButtonClick(Sender: TObject);
  begin
    case BASS_ChannelIsActive(SoundStream) of
      BASS_ACTIVE_PLAYING:
      begin
        if BASS_Pause then
          MusicButton.Caption := 'Sound On';
      end;
      BASS_ACTIVE_PAUSED:
      begin
        if BASS_Start then
          MusicButton.Caption := 'Sound Off';
      end;
    end;
  end;