replace in opening quotations

node6.html

@@ -75,7 +75,7 @@ process, and analyze musical sounds, a practice which came into its modern form
 in the years 1948-1952, but whose technological means and artistic uses have
 undergone several revolutions since then.  Nowadays most electronic music is
 made using computers, and this book will focus exclusively on what used to be
-called ``computer music", but which should really now be called  ``electronic
+called "computer music", but which should really now be called  "electronic
 music using a computer".
 
 <P>
@@ -117,7 +117,7 @@ appears in [<A
  HREF="node202.html#r-strawn85">Str85</A>, pp. 1-68].
 
 <P>
-Although the ``level" of mathematics is not high, the mathematics itself is
+Although the "level" of mathematics is not high, the mathematics itself is
 sometimes quite challenging.  All sorts of cool mathematics is in the reach of
 any student of algebra or geometry.  In the service of computer music, for
 instance, we'll run into Bessel functions, Chebychev polynomials, the Central
@@ -127,7 +127,7 @@ Limit Theorem, and, of course, Fourier analysis.
 You don't need much background in music as it is taught in the West; in
 particular, Western written music notation is not needed.  Some elementary bits
 of Western music theory are used, such as the tempered scale, the A-B-C system
-of naming pitches, and terms like ``note" and ``chord".  Also you should be
+of naming pitches, and terms like "note" and "chord".  Also you should be
 familiar with terms of musical acoustics such as sinusoids, amplitude,
 frequency, and the overtone series.