% lowpass   // Low-pass filter music.
lambda = 0.97;  % Higher lambda = more smoothing.
ylow_prev = 0;
ylow = zeros(length(y),1);
for index = 1:length(y)
  ylow_next = ylow_prev * lambda +y(index);
  ylow(index) = ylow_next;
  ylow_prev = ylow_next;
end
ylow = ylow * sum(y.^2)/sum(ylow.^2);
y = ylow;
louder
louder
louder

