uses
  Gorilla.Audio.FMOD,
  Gorilla.Audio.FMOD.Sound,
  Gorilla.Audio.FMOD.Channel;

procedure TForm1.FormShow(Sender: TObject);
var LSound : IGorillaFMODSound;
    LChannel : IGorillaFMODChannel;
    LClock, LPClock : UInt64;
begin
  {...}
  LChannel := FFMOD.PlaySound(LSound, nil, false, 0);
  if Assigned(LChannel) then
  begin
    LChannel.GetDSPClock(LClock, LPClock);
    LChannel.AddFadePoint(LPClock, 0.0);
    LChannel.AddFadePoint(LPClock + 48000, 1.0);
  end;  
end;