naming output files (maybe a feature request?)

[Kieren MacMillan]

Hi all,

Is there any way to explicitly name the output files of a score?

This is particularly a problem for me when I have multiple \book-s in  
a single .ly file -- the default file naming (file-1.pdf, file-2.pdf)  
is not very helpful. I would prefer to do something like:

\book
{
    #(set-output-name "VocalScore")
    \score
    {
        << \vocalMusic >>
    }
}

\book
{
    #(set-output-name "PianoVocalScore")
    \score
    {
        <<
            \new Staff << \vocalMusic >>
            \new PianoStaff << \pianoMusic >>
       >>
    }
}

which would generate the files VocalScore.pdf and  
PianoVocalScore.pdf. Is there anything like this mechanism? [I did do  
a fairly long search through the list and docs, but wasn't able to  
turn up anything...]

Thanks!
Kieren.