[xsl] XSLT grouping problem

I have xml input files in the following format

Music categoryFilter="rock,pop,r&b,country,latin" yearsFilter="97,98,99,"
        Singer
                Album
                        Song  categoryFilter="rock"

I have filters on category and years at each level. (I may or may not have at 
each 
level)
The complete list of categories and years are stored in another xml file.
I need to convert this into another xml with the filters as the parent elements 
and 
everything else
underneath it.
Something like

Year name="97"
        Category name="rock"
                Singer
                        Album
                                Song
                
If I have a categoryFilter at two levels, we can assume that the parent 
contains a 
superset list of
categories and if a level does not have a filter, we can assume it has the same 
filters as the parent.
                
Here's an example:

filters.xml
<Filters>
        <CategoryFilters>
                <Category>rock</Category>
                <Category>pop</Category>
                <Category>r&b</Category>
                <Category>country</Category>
                <Category>latin</Category>
        </CategoryFilters>
        <YearsFilter>
                <Year>00</Year> 
                <Year>01</Year> 
                <Year>02</Year> 
                <Year>03</Year> 
                <Year>04</Year> 
                <Year>05</Year> 
        </YearsFilter>

input.xml
        <Music categoryFilter="rock,pop,r&b,country,latin" 
yearsfilter="00,01,02,03,04,05,06"
                <Singer name="Shakira" categoryFilter="pop,rock,latin" 
yearsfilter="00,01,02,04,05,06">
                        <Album name="Laundry Service" yearsFilter="01" 
categoryFilter="latin">
                                <Song name="Objection (Tango)"/>
                                <Song name="xyz"/>
                        </Album>
                        <Album name="Oral Fixation" yearsFilter="05,06">
                                <Song name="...."/>
                        </Album>
                </Singer>
                <Singer name="Ricky Martin categoryFilter="" 
yearsFilter="00,04,05,06">
                        <Album name="I Don't Care" yearsFilter="05">
                                <Song name="...."/>
                        </Album>
                </Singer>
        </Music>

Expected Output:        
<Year name="05">
        <Category name="latin">
                        <Singer name="Shakira">
                                <Album name="Oral Fixation">
                                        <Song name="..."/>
                                </Album>
                        </Singer>
        </Category>                     
<Year name="06">
        <Category name="latin">
                        <Singer name="Shakira">
                                <Album name="Oral Fixation">
                                        <Song name="..."/>
                                </Album>
                        </Singer>
        </Category>                     
<Year name="01">
        <Category name="latin">
                        <Singer name="Shakira">
                                <Album name="Laundry Service">
                                        <Song name="Objection (Tango)"/>
                                </Album>
                        </Singer>
        </Category>                     

How do I convert this ?
I am new to XSLT and have gone thru' several mails and I realise I need to use 
grouping (for-each-group) twice, once for category and one for year.
Although the structure may not make sense, I do not control the DTD for the 
input 
or the output.

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