fix typos, add more roman docs.

documentation/source/usersGuide/usersGuide_13_music21object2.ipynb

@@ -587,7 +587,7 @@
    "source": [
     "### getContextByClass()\n",
     "\n",
-    "This is an extremely powerful tool -- you might not use it often, but be assured that `music21` is using it on your behalf all the time when sophisticated analysis is involved.  It finds the active element matching a certain class preceeding the element.  Let me demonstrate:"
+    "This is an extremely powerful tool -- you might not use it often, but be assured that `music21` is using it on your behalf all the time when sophisticated analysis is involved.  It finds the active element matching a certain class preceding the element.  Let me demonstrate:"
    ]
   },
   {
@@ -803,7 +803,7 @@
     "\n",
     "Then if that fails, it will look at the score as a whole, beginning at offset 35 and working backwards, but only looking at things that are at the score level, not looking at elements within other parts. There may be scores where for instance, expressive markings appear at the Score level. This will find them.\n",
     "\n",
-    "Related to `.getContextByClass()` is `.getAllContextsByClass()` which is a generator that returns each preceeding context."
+    "Related to `.getContextByClass()` is `.getAllContextsByClass()` which is a generator that returns each preceding context."
    ]
   },
   {

documentation/source/usersGuide/usersGuide_61_trees.ipynb

@@ -639,9 +639,7 @@
   {
    "cell_type": "markdown",
    "metadata": {},
-   "source": [
-    "And using this information they can get the verticalities just preceeding or following them:"
-   ]
+   "source": "And using this information they can get the verticalities just preceding or following them:"
   },
   {
    "cell_type": "code",

music21/roman.py

@@ -3058,7 +3058,6 @@ def adjustMinorVIandVIIByQuality(
         >>> rn.frontAlterationAccidental
         <music21.pitch.Accidental sharp>
 
-
         >>> rn = roman.RomanNumeral()
         >>> rn.scaleDegree = 6
         >>> rn.impliedQuality = 'major'
@@ -3068,6 +3067,9 @@ def adjustMinorVIandVIIByQuality(
         >>> rn.frontAlterationAccidental is None
         True
 
+        Note that this function is not called in parsing, but a private function having the
+        guts of this function is called.
+
         * Changed in v6.4: public function became hook to private function having the actual guts
         '''
         unused_workingFigure = self._adjustMinorVIandVIIByQuality('', useScale)
@@ -3104,6 +3106,11 @@ def _adjustMinorVIandVIIByQuality(
         '''
         def sharpen(wFig: str) -> str:
             changeFrontAlteration(interval.Interval('A1'), 1)
+
+            # changing the working figure is important if the private function is called
+            # on its own (as happens in parse figure).  It doesn't have any effect if
+            # calling the public adjustMinorVIandVIIByQuality.
+
             # If root is in the figure, lower the root to avoid double-sharpening
             if '##' in wFig:
                 wFig = wFig.replace('##8', '#8')