Fix #128: clarify effect of setting the value attribute with respect …

…to equivalent parameter automation action.

index.html

@@ -1556,6 +1556,9 @@ <h2 id="AudioParam">The AudioParam Interface</h2>
       when there are any automation events scheduled then it will be ignored and
       no exception will be thrown.
     </p>
+    <p>
+      The effect of setting this attribute is equivalent to calling <code>setValueAtTime()</code> with the current <code>AudioContext</code>'s <code>currentTime</code> and the requested value. Subsequent accesses to this attribute's getter will return the same value.
+    </p>
   </dd>
   <dt> readonly attribute float defaultValue </dt>
   <dd>