How to change the volume

Problem/Question/Abstract:

How can I change the volume?

Answer:

procedure SetVolume(X: Word);
var
  iErr: Integer;
  i: integer;
  a: TAuxCaps;
begin
  for i := 0 to auxGetNumDevs do
  begin
    auxGetDevCaps(i, Addr(a), SizeOf(a));
    if a.wTechnology = AUXCAPS_CDAUDIO then
      break;
  end;

  // Sets volume equally for left and right channels.
  // VOLUME := LEFT * $10000 + RIGHT * 1 (or the other way? :)

  iErr := auxSetVolume(i, (X * $10001));
  if (iErr = 0) then
    ShowMessage('No audio devices are available!');
end;

function GetVolume: Word;
var
  iErr: Integer;
  i: integer;
  a: TAuxCaps;
  vol: word;
begin
  for i := 0 to auxGetNumDevs do
  begin
    auxGetDevCaps(i, Addr(a), SizeOf(a));
    if a.wTechnology = AUXCAPS_CDAUDIO then
      break;
  end;
  iErr := auxGetVolume(i, addr(vol));
  GetVolume := vol;
  if (iErr = 0) then
    ShowMessage('No audio devices are available!');
end;

You'll have to modify AUXCAPS_CDAUDIO to whatever suits
(check out available values via the Ctrl+Space shortcut in Delphi 3)