My experience was with large non-const data. For const data, I would have thought it would load the section like code; just once. I did not know that the compiler would use a .text. for init data. That just doubles the memory usage and adds a needless copy operation. Looking at the compiler manual, the PERSISTENT pragma might result in one copy, eg.
#pragma PERSISTENT (big_array);
Otherwise, I think you might have to resort to assembler to define your data. The lack of audio might be another problem unrelated to the DDR location. If it possible, maybe try scaling down the big array till you get audio.
I've only seen file operations used in the spi flash writer project. Never used it myself. That should work but that would mean your product is dependent upon a JTAG and CCS to be always connected. I find it amazing that the target can open a file on the host. I suspect such a solution would also be extremely slow.
You should unverify my post. Unverified threads attract more attention. You've reached the limit of my knowledge. Hopefully someone more knowledgable will comment.