square note heads for cluster

[andersvi]

Hello.

I need to notate some clusters using squared rhythmic note-heads,
something along the lines of this figure:

aaa.png
Description: PNG image

Its possible to set up a music-function to generate a square markup
based on the pitches of a chord, but i think this way of notation
clusters is pretty standard so maybe someone already have something
lying around?

If not, is there a good list of various 'ly:' -prepended info-grabbing
functions returning ambitus, notes, pithces, note-lines, y-positiions
and the like?

Thanks.

-anders