-index :duration dur)))
    (do ((i start (+ i 1)))
        ((= i end))
      (outa i (* (env ampf)                       ; amplitude env
                 (oscil cr (* (env indf)          ; carrier + modulation env
                              (oscil md))))))))   ; modulation
</pre>
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<p>I put an envelope on the fm-index ("indf" above) to try out dynamic spectra ("dynamic" means 
"changing" here).  For now, don't worry too much about the actual side band amplitudes.  They
will not always match Cho