re class="indented">
(with-sound () (fm 0 1.0 400 .5 0.25 4.0))
</pre>

<p>we end up with the same perceived pitch because the sidebands are still at multiples of 100 Hz.
</p>

<pre class="indented">
(with-sound () (fm 0 1.0 400 .5 1.1414 4.0))
</pre>

<p>has inharmonic sidebands.  Most real sounds seem to change over the course of a note, and it was at one time thought that most 
of this change was spectral.  To get a changing spectrum, we need only put an envelope on the fm-index:
</p>

<pre class="indent