Sizing noteheads in a chord construct?

[Shamus]

Is it possible to shrink noteheads in a chord context such as <c e g> so
that say, the c is normal sized while the e and g are smaller? I've
tried <c \small e g \normalsize> but lily doesn't like that. I've tried
to use \partcombine to do this, but it only works with two distinct
voices and putting { c } in one part and { <e g> } in the other doesn't
combine the c with the e and the g (why would it? they're separate
contexts, no?).

I'm trying to write a melody line with supporting harmonies in smaller
notes AND attached to the same stem as the melody in order to make the
melody line clear and conserve space on my chart. Version 2.8.2, and the
documentation and tutorials have exactly nothing to say on the subject.

-- Shamus