>GATE</code> is -1, there is an
        immediate cutoff. If <code>GATE</code> is less than -1, there is a
        release stage with a custom duration <code>(- -1.0 GATE)</code>.
      </p>

      <p>
        The fourth argument of <code>ENVELOPE</code> is <code>DONE-ACTION</code>,
        a one-argument function called at the end of the envelope. The function
        argument is the DSP node. In the previous example, the DSP terminates at
        the end of the envelope, so we cannot retrig the envelope a