replace in opening quotations

node71.html

@@ -136,7 +136,7 @@ to implement the summing bus:
  WIDTH="69" HEIGHT="39" ALIGN="MIDDLE" BORDER="0"
  SRC="img386.png"
  ALT="\fbox{ \texttt{catch\~}}">:
-<A NAME="4908"></A>define and output a summing bus.  The creation argument (``sum-bus" in this example)
+<A NAME="4908"></A>define and output a summing bus.  The creation argument ("sum-bus" in this example)
 gives the summing bus a name so that <TT>throw~</TT> objects below can refer
 to it.  You may have as many summing busses  (and hence <TT>catch~</TT> objects)
 as you like but they must all have different names.
@@ -153,8 +153,8 @@ as you like but they must all have different names.
 use.
 
 <P>
-The control interface is crude: number boxes control the ``fundamental"
-frequency of the bell and its duration.  Sending a ``bang" message to 
+The control interface is crude: number boxes control the "fundamental"
+frequency of the bell and its duration.  Sending a "bang" message to 
 the <TT>s trigger</TT> object starts a note.  (The note then decays over
 the period of time controlled by the duration parameter; there is no
 separate trigger to stop the note).  There is no amplitude
@@ -190,9 +190,9 @@ frequency and the relative frequency.
 </LI>
 </OL>
 Inside the <TT>partial</TT> abstraction, the amplitude is simply taken
-directly from the ``$1" argument (multiplying by 0.1 to adjust for
+directly from the "$1" argument (multiplying by 0.1 to adjust for
 the high individual amplitudes); the duration is calculated from the
-<TT>r duration</TT> object, multiplying it by the ``$2" argument.
+<TT>r duration</TT> object, multiplying it by the "$2" argument.
 The frequency is computed as <IMG
  WIDTH="48" HEIGHT="30" ALIGN="MIDDLE" BORDER="0"
  SRC="img390.png"