function eval_lfo()

L = 10000;
fs = 44100;
fstart = 44;
fend = 400;
df = (fend-fstart)/L;

ip = 0 % phase of the first output sample in radians

% Init

% Loop
f = fstart;
fchg = 1;

y1=sin(ip-f*pi / fs);
y2=sin(ip-2*f*pi / fs);

for n=1:L,

if fchg == 1,
    b1 = 2.0 * cos(f*pi / fs);
    fchg = 1000;
end;

y0 = b1*y1 - y2;
y2 = y1;
y1 = y0;

fchg = fchg - 1;

lfo(n) = y0;
f = f + df;

close all

end;

figure;
plot(1:L, lfo); grid;

wavwrite(0.5*lfo, fs, 'lfo.wav');