How to mute audio (change volume) with BASS library in Inno Setup - inno-setup

Question

This code from Bass Audio Library on/off Button does "Pause", how to change it to "Mute"?
What should I change?
const
BASS_SAMPLE_LOOP = 4;
BASS_ACTIVE_STOPPED = 0;
BASS_ACTIVE_PLAYING = 1;
BASS_ACTIVE_STALLED = 2;
BASS_ACTIVE_PAUSED = 3;
BASS_UNICODE = $80000000;
BASS_CONFIG_GVOL_STREAM = 5;
const
#ifndef UNICODE
EncodingFlag = 0;
#else
EncodingFlag = BASS_UNICODE;
#endif
type
HSTREAM = DWORD;
function BASS_Init(device: LongInt; freq, flags: DWORD;
win: HWND; clsid: Cardinal): BOOL;
external 'BASS_Init#files:bass.dll stdcall';
function BASS_StreamCreateFile(mem: BOOL; f: string; offset1: DWORD;
offset2: DWORD; length1: DWORD; length2: DWORD; flags: DWORD): HSTREAM;
external 'BASS_StreamCreateFile#files:bass.dll stdcall';
function BASS_Start: BOOL;
external 'BASS_Start#files:bass.dll stdcall';
function BASS_Pause: BOOL;
external 'BASS_Pause#files:bass.dll stdcall';
function BASS_ChannelPlay(handle: DWORD; restart: BOOL): BOOL;
external 'BASS_ChannelPlay#files:bass.dll stdcall';
function BASS_SetConfig(option: DWORD; value: DWORD ): BOOL;
external 'BASS_SetConfig#files:bass.dll stdcall';
function BASS_ChannelIsActive(handle: DWORD): DWORD;
external 'BASS_ChannelIsActive#files:bass.dll stdcall';
function BASS_Free: BOOL;
external 'BASS_Free#files:bass.dll stdcall';
var
SoundStream: HSTREAM;
SoundCtrlButton: TNewButton;
procedure SoundCtrlButtonClick(Sender: TObject);
begin
case BASS_ChannelIsActive(SoundStream) of
BASS_ACTIVE_PLAYING:
begin
if BASS_Pause then
SoundCtrlButton.Caption :=
ExpandConstant('{cm:SoundCtrlButtonCaptionSoundOn}');
end;
BASS_ACTIVE_PAUSED:
begin
if BASS_Start then
SoundCtrlButton.Caption :=
ExpandConstant('{cm:SoundCtrlButtonCaptionSoundOff}');
end;
end;
end;
procedure InitializeWizard;
begin
ExtractTemporaryFile('tune.mp3');
if BASS_Init(-1, 44100, 0, 0, 0) then
begin
SoundStream := BASS_StreamCreateFile(False,
ExpandConstant('{tmp}\tune.mp3'), 0, 0, 0, 0,
EncodingFlag or BASS_SAMPLE_LOOP);
BASS_SetConfig(BASS_CONFIG_GVOL_STREAM, 2500);
BASS_ChannelPlay(SoundStream, False);
SoundCtrlButton := TNewButton.Create(WizardForm);
SoundCtrlButton.Parent := WizardForm;
SoundCtrlButton.Left := 8;
SoundCtrlButton.Top := WizardForm.ClientHeight -
SoundCtrlButton.Height - 8;
SoundCtrlButton.Width := 40;
SoundCtrlButton.Caption :=
ExpandConstant('{cm:SoundCtrlButtonCaptionSoundOff}');
SoundCtrlButton.OnClick := #SoundCtrlButtonClick;
end;
end;
procedure DeinitializeSetup;
begin
BASS_Free;
end;

Answer 1

To control volume level, use the BASS_SetConfig with option set to:
BASS_CONFIG_GVOL_STREAM for "stream", created e.g. using the BASS_StreamCreateFile;
BASS_CONFIG_GVOL_MUSIC for "music", created e.g. using BASS_MusicLoad.
The SoundCtrlButtonClick is replacement for the pause/resume implementation of the same-named function from your question.
var
Muted: Boolean;
procedure SoundCtrlButtonClick(Sender: TObject);
begin
if not Muted then
begin
if BASS_SetConfig(BASS_CONFIG_GVOL_STREAM, 0) then
begin
SoundCtrlButton.Caption := 'unmute';
Muted := True;
end;
end
else
begin
if BASS_SetConfig(BASS_CONFIG_GVOL_STREAM, 2500) then
begin
SoundCtrlButton.Caption := 'mute';
Muted := False;
end;
end;
end;