> I'm trying not to use keys

Why? This is essentially what they are there for.

   <xsl:for-each select="//Artist[@festival = .]">
 
  I'm guessing that the value of "." is lost because I'm beginning at the
  top of the document again.

no, . inside a predicate always means the node to which the predicate is
being applied, so the Artist node here, this is a general feature, not a
result of the xpath starting with  /. You probably want current().
But //Artist[@festival =  anything] is _exactly what keys are designed
to make efficient.

use 
<xsl:for-each key select="key('f',.)">

where your key is

<xsl:key match="Artist" use="@festival"/>

This is simpler to write (no need for current() or //) and can be 
thousands of times faster when run on a large document.

David

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