IIRC, the early Still is much more interesting as he was, once more IIRC, studying with Varese. Then he got into more folk forms and truthfully his talent deserted him - blues posturing, very shallow use of the vernacular.
The afformentioned (in another thread) Coleridge Taylor Perkinson is head and shoulders above Still in his ability to channel traditional forms and transform them into something personal and expressive. No comparison, from where I sit.
I have not, I think, however, heard the Fourth.