Yes, every interview/article I've read about John Martyn mentions this. I believe that there's the chorus of Solid Air on the 4 LP box set of Nick's recordings that Island release in the late '70's, printed on the booklet (give me an excuse to check out my copy again). I think in these days, Nick Drake would have been diagnosed with depression and I think that's the gist of John Martyn's song. I understand that John Martyn doesn't talk much about Nick Drake these days, understandably. My interpretation of the words is that it's more of a mood song, than a linear song. Sort wishing to help, but knowing there's not much you can do.