 Feigenbaum behavior thereafter.  I guess these
things are just called iterated functions or fixed-point equations.
-->

<!-- LATEX
\large
\begin{align*}
&z \cos(z \cos(z\cdots)) = 2 \sum_{k=0}^{\infty} (-1)^{k} \frac{J_{2k+1}((2k+1)z)}{2k+1} & z<1.27 \\
\end{align*}
-->


<div class="spacer"></div>
<div class="greenish">feedback FM: sin(x=sin(x))</div>

<p>A similar trick comes up in feedback FM used in some synthesizers. Here the output of the modulator
is fed back into its input:
</p>

<pre class="indent