Piano flash cards

[George Geller]

How hard would it be to make lilypond output piano flash cards for
beginning students?  The cards will print six to an 8 1/2 by 11 inch
page and show the treble and bass clefs with a single note or maybe a
chord or interval.

I haven't found where to set the page size in lilypond or how to combine
a number of "documents" to print on a single page.

I'm a good programmer, so I could modify the code if need be.

Thanks, George