I'm thinking that it would be possible to put language in the
copyright statement in which the composer recommends royalty payments from
groups that perform the work without requiring it. In fact, "royalty" may
not be the right word for such payments, but I'll continue to use it for
the time being.
I'm not a music professional (nor am I aiming to be), so perhaps
I'm speaking from ignorance, but I can't imagine that performing groups
with adequate resources would stiff the composer and not pay the
recommended royalty. Such a recommendation wouldn't be binding, though,
which'd keep the music free.
As far as control of recordings is concerned, there could be
similar language recommending royalty payment from those who'd put
recordings of free music for sale without requiring it. An unscrupulous or
fly-by-night recording company might see fit to ignore the recommendation,
but principled companies would support their content providers. (And use
copyright of cover art and such to stave off unscrupulous companies that'd
otherwise undercut them.)
Of course, compressed audio formats and the increased networking
of the world are already changing the paradigm under which recordings are
distributed...
Matt Hiller