Function to mix audio channels

mix.pas

procedure Mix(ADest: PByte; ASources: array of PByte; ASize, ALength: Integer);
var
  i, j: Integer;
begin
  for i := 0 to (ALength - 1) div ASize do
    for j := 0 to Length(ASources) - 1 do
    begin
      Move(ASources[j]^, ADest^, ASize);

      Inc(ADest, ASize);
      Inc(ASources[j], ASize);
    end;
end;