A way to fake including multiple stylesheets and choosing which to use

conditional-include.xslt

<?xml version="1.0" encoding="utf-8" ?>
<xsl:stylesheet
	version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
	xmlns:umb="urn:umbraco.library"
	exclude-result-prefixes="umb"
>

	<xsl:output method="xml" indent="yes" omit-xml-declaration="yes" />

	<xsl:param name="currentPage" />
	<xsl:variable name="siteRoot" select="$currentPage/ancestor-or-self::Website" />
	
	<xsl:variable name="guitarStyle" select="/macro/playingStyle" />
	
	<xsl:template match="/">
		<!-- These are mutually exclusive -->
		<xsl:apply-templates select="$currentPage[$guitarStyle = 'blues']" mode="blues" />
		<xsl:apply-templates select="$currentPage[$guitarStyle = 'metal']" mode="metal" />
		<xsl:apply-templates select="$currentPage[$guitarStyle = 'jazz']" mode="jazz" />
	</xsl:template>
	
	<!-- Including all styles of awesome guitar playing -->
	<xsl:include href="_guitarStyles_blues.xslt" />
	<xsl:include href="_guitarStyles_metal.xslt" />
	<xsl:include href="_guitarStyles_jazz.xslt" />

</xsl:stylesheet>