hly speaking, there are fm-index+1 
significant sidebands on each side of the carrier, so our total bandwidth is more or less
</p>

<pre class="indented">
2 * modulator-frequency * (fm-index + 1)
</pre>

<p>This is a good approximation &mdash; 99% of the signal power is within its limits.  To turn that around, we can 
reduce the danger of aliasing by limiting the FM index to approximately (srate/2 - carrier_frequency) / modulator_frequency;
use srate/4 to be safer.  (Mr Carson's opinion of FM: "this method 