This is a dirt-cheap quadratic approximation of a sine:
B = 4/$PI;
C = -4/($PI*$PI);
function quicksine(x) local(y)
(
y = B*x + C*x*abs(x);
y = 0.225 * (y * abs(y) - y) + y;
y;
);
Haven't listened to it, but it does pretty well as an LFO.
NB: Only valid between -PI and PI. Discovered here:
http://forum.devmaster.net/t/fast-an...ne-cosine/9648
I recommend following the link, there are varying levels of accuracy to be had with this approximation, depending on what you're optimising for.