title: Muenchian Grouping - group within a node, not within the entire document
body: <p>I'm trying to use Muenchian grouping in my XSLT to group matching nodes, but I only want to group within a parent node, not across the entire source XML document. </p>
  
  <p>Given XSLT and XML as follows (apologies for the length of my sample code): </p>
  
  <p><strong>XSLT</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl"&gt; 
   &lt;xsl:output method="html" indent="yes"/&gt;
  
   &lt;xsl:key name="contacts-by-surname" match="contact" use="surname" /&gt;
   &lt;xsl:template match="records"&gt;
    &lt;xsl:for-each select="contact[count(. | key('contacts-by-surname', surname)[1]) = 1]"&gt;
     &lt;xsl:sort select="surname" /&gt;
     &lt;xsl:value-of select="surname" /&gt;,&lt;br /&gt;
     &lt;xsl:for-each select="key('contacts-by-surname', surname)"&gt;
      &lt;xsl:sort select="forename" /&gt;
      &lt;xsl:value-of select="forename" /&gt; (&lt;xsl:value-of select="title" /&gt;)&lt;br /&gt;
     &lt;/xsl:for-each&gt;
    &lt;/xsl:for-each&gt;
   &lt;/xsl:template&gt;
  &lt;/xsl:stylesheet&gt;
  </code></pre>
  
  <p><strong>XML</strong></p>
  
  <pre><code>&lt;root&gt;
   &lt;records&gt;
    &lt;contact id="0001"&gt;
     &lt;title&gt;Mr&lt;/title&gt;
     &lt;forename&gt;John&lt;/forename&gt;
     &lt;surname&gt;Smith&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0002"&gt;
     &lt;title&gt;Dr&lt;/title&gt;
     &lt;forename&gt;Amy&lt;/forename&gt;
     &lt;surname&gt;Jones&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0003"&gt;
     &lt;title&gt;Mrs&lt;/title&gt;
     &lt;forename&gt;Mary&lt;/forename&gt;
     &lt;surname&gt;Smith&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0004"&gt;
     &lt;title&gt;Ms&lt;/title&gt;
     &lt;forename&gt;Anne&lt;/forename&gt;
     &lt;surname&gt;Jones&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0005"&gt;
     &lt;title&gt;Mr&lt;/title&gt;
     &lt;forename&gt;Peter&lt;/forename&gt;
     &lt;surname&gt;Smith&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0006"&gt;
     &lt;title&gt;Dr&lt;/title&gt;
     &lt;forename&gt;Indy&lt;/forename&gt;
     &lt;surname&gt;Jones&lt;/surname&gt;
    &lt;/contact&gt;
   &lt;/records&gt;
   &lt;records&gt;
    &lt;contact id="0001"&gt;
     &lt;title&gt;Mr&lt;/title&gt;
     &lt;forename&gt;James&lt;/forename&gt;
     &lt;surname&gt;Smith&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0002"&gt;
     &lt;title&gt;Dr&lt;/title&gt;
     &lt;forename&gt;Mandy&lt;/forename&gt;
     &lt;surname&gt;Jones&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0003"&gt;
     &lt;title&gt;Mrs&lt;/title&gt;
     &lt;forename&gt;Elizabeth&lt;/forename&gt;
     &lt;surname&gt;Smith&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0004"&gt;
     &lt;title&gt;Ms&lt;/title&gt;
     &lt;forename&gt;Sally&lt;/forename&gt;
     &lt;surname&gt;Jones&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0005"&gt;
     &lt;title&gt;Mr&lt;/title&gt;
     &lt;forename&gt;George&lt;/forename&gt;
     &lt;surname&gt;Smith&lt;/surname&gt;
    &lt;/contact&gt;
    &lt;contact id="0006"&gt;
     &lt;title&gt;Dr&lt;/title&gt;
     &lt;forename&gt;Harry&lt;/forename&gt;
     &lt;surname&gt;Jones&lt;/surname&gt;
    &lt;/contact&gt;
   &lt;/records&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p><strong>RESULT</strong></p>
  
  <pre><code>Jones,
  Amy (Dr)
  Anne (Ms)
  Harry (Dr)
  Indy (Dr)
  Mandy (Dr)
  Sally (Ms)
  
  Smith,
  Elizabeth (Mrs)
  George (Mr)
  James (Mr)
  John (Mr)
  Mary (Mrs)
  Peter (Mr)
  </code></pre>
  
  <p>How do I group within each <code>&lt;records&gt;</code> and achieve this result:</p>
  
  <pre><code>Jones,
  Amy (Dr)
  Anne (Ms)
  Indy (Dr)
  
  Smith,
  John (Mr)
  Mary (Mrs)
  Peter (Mr)
  
  Jones,
  Harry (Dr)
  Mandy (Dr)
  Sally (Ms)
  
  Smith,
  Elizabeth (Mrs)
  George (Mr)
  James (Mr)
  </code></pre>