<xsl:key name="workcds" match="cd/playlist/work" use="." /> 

<xsl:for-each  select="cd/playlist/work">
<work>
  <xsl:attribute name="id">
    <xsl:value-of select="generate-id(.)"/>
  </xsl:attribute>
  <xsl:attribute name="first">
    <xsl:value-of select="generate-id(key('workcds',.)[1])"/>
  </xsl:attribute>
  <xsl:value-of select="."/>
</work>
</xsl:for-each>
. . .
<work id="d0e43778" first="d0e43778">Waiter, make mine blues</work> 
<work id="d0e43781" first="d0e7452">What is this thing called love?</work> 
<work id="d0e43807" first="d0e17267">Opus one</work>