Discuss this with Robert Greenburg, or Steven Gryc (my cousin). In the former's case, he has come out saying in no uncertain terms that modern legal issues, hard for 18th and 19th century musicians to ever have imagined, have circumscribed the free and wide dissemination of modern art music. In my cousin's case, he was not allowed to send out any recordings to anyone for any reason, without first paying royalties to the symphony musicians.
All that you tell us here about Mr Greenburg's statement is an unsupported opinion; he does not say (or you do not report him as saying) on what specific grounds he believes this to be the case; that's the first thing that I'd ask him were I inded to discuss it with him. In your cousin's case, as I wrote previously, the same situation would have applied (if the orchestral musicians' contracts provided for this) to a recording of them playing anything, not just copyright music.
The big-buck legalese that has permeated hip-hop, rock n' roll, and country has set precedents for art music that do not help it gain in popularity. Admittedly, this is only part of the reason modern music has had a hard time gaining popularity, but it is a real issue.
There is no such "big-buck legalese"; that's a myth. If there were, how would you account for the many hundreds of thousands of CDs of copyright music being issued regularly or the broadcasts of copyright music all over the world? In any case, we're talking
copyright music here, not just "modern music" (i.e. music written by living or recently deceased composers).
Copyright music includes Rachmaninov (just!), Bartók, Webern, Strauss, Sibelius, Vaughan Williams, Stravinsky, Shostakovich, Britten and many so many more composers who have been dead for a long time.
Composers' Estates can indeed occasionally be obstructive, but that's hardly the norm where copyright music is concerned. In any case, how would you seek to ensure that even this couldn't happen? The only way would be to dispense with intellectual property rights altogether, which would require prior agreement from every country that recognises them; the protracted proceedings that this would involve - even if such global agreement in principle could first be secured - would really give big-shot lawyers a lot of work, human rights lawyers in particular, the cost in both time and money would be immense and the likelihood is that the lawyers' work would ultimately guarantee that wholesale disposal of such rights would fail.
Best,
Alistair