I came on this interesting page today, with a chart characterizing instruments in general, and free-reed instruments in particular:

The Classical Free-Reed, Inc.
The Free-Reed Family: A Brief Description Taxonomy of Musical Instruments, By Henry Doktorski
and
The Free-Reed Family of Aerophones, By Diarmuid Pigott (his page, referred to here and linked on an old Mudcat harmonium thread, seems to be gone)

Clicky

Wow.

While I'm at it, that site didn't quite explain the difference between a "free reed" and a "beating reed" clearly enough, and I found this site did:
What is a free reed

and I reached that one via the Wikipedia entry on Free reed aerophone.

~ Becky in Tucson
(I looked around to see about adding this to another thread, but didn't want to limit viewers to those interested one instrument or another.)