SFist interviews Michael Tilson Thomas:
He [Henry Brant] actually knew Ives. He passed out very recently in his late nineties, so he had a connection back to Ives himself. Henry Brant was a great orchestrator. He made his living by orchestrating shows and movies and various things. In a way, he was like a colleague of his who was a also fan of Charles Ives, Bernard Herman, who wrote all the great Hitchcock movie scores.
There were the kind of guys who were on Ives' side, along with Lou Harrison, John Kirkpatrick. In the days Ives was considered a kind of lunatic, these were the major guys who said: "No, he's not a lunatic! He's a major inventive genius, and what can we do to make his work better known." What Brant did, for over fifty years, was to orchestrate this Concord sonata. Only recently he completed it, but the piece is still performed very little.
Not sure what MTT meant in that first paragraph.
One doesn't exactly think of the Concord as a polyphonic work, but Brant finds its polyphony and accentuates it. Despite the complexity, grandeur, and mass dissonances, the lightness of his scoring, its almost chamber character, is the dominant impression.
The San Francisco Symphony performs the work this week. And the SFS 50% off ticket sale ends Friday for those so inclined.