There's not too much to glean from these lyrics. He's lonely and sad, so he "plays in the rain." I think playing in the rain represents making the best of a bad situation - it's raining, but he can still play in the midst of it all. Lyrically, I think that's what it's about. Musically, it sounds like Lindsey had a synthesizer with a button labelled "water" and went to town, literally playing around on it!
OK, OK, I'm sure it was 1000 times more sophisticated than that, with magnificent equipment and carefully and painstakingly blended sounds, but I expect more from a song than a cerebral exercise in sound manipulation! Like a real melody. Perhaps that's plebeian of me, so sue me.
Your mother would never let you play in the rain...it was forbidden. As an adult, you are considered strange or crazy if you play in the rain. Perhaps, just perhaps, there is more to these two pieces than what meets the ears...
He is asking someone if they can play in the rain...it was forbidden when they were kids, and now as adults, they would be going against convention to play in it, ignoring what anyone else thinks.
Also add the idea that rain could be synonymous with tears. Possibly his, and he is asking this person if they can play despite the rain, despite his sadness. Asking if they can put up with his pain and still be with him.
Part I isn't all that bad musically either. To be sure it is experimental, but I think that it not only reinforces the lyrics, but also nicely sets up Part II (I personally wish that they were put together as one track). There is a lot of fear and suspense in Part I...a lot of doubt and maybe hopelessness and the way the lyrics are sung, it is almost confessional.
Part II kicks in melodically if not powerfully. There is a lot of passion and anger both vocally and instrumentally. Very confident. Perhaps he got to play in the rain.
Rain and the sea seem to mean something to both Lindsey and Stevie (see Trouble in Shangri-La, Crystal, Outside the Rain, Dreams, Surrender the Rain) like the way they both keep referring to "night" in their songs.
Water is in nature, it is in us, but people have drowned in it. So in that sense it makes us similar to the world around us but when it isn't under our control it can be fatal. I think this image is appropriate for how Lindsey looks at himself. The depth of his emotions is what makes his music so good. Like the water they are natural and thus have the limitless energy that nature has. But their strength could consume him and make him go insane (hehehe) unless he keeps them under his control. What makes him special is what can hurt him the most and I think he knows that and this makes him frustrated and lonely.
So then why does he want to "play in the rain"? I think the only time he was able to do so and not feel alone was when he was with Stevie. She shared the spiritual depth that put her in the "rain" as well, and then they saw each other. So where he had been "lonely" and "crying" he no longer felt alone or sad. But neither one could give up their control which kept them from being consumed by the "rain" and the anger and hurt he feels at having lost having her in the "rain" comes through in the second part of Playing in the Rain. I think the first part of the song is softer because it is representing the time when he was with Stevie. I know this album is dedicated to Carol Ann, but I think the fact that it is in two parts (like You and I Parts I,II) signifies these emotions over time, time that he had not had with Carol Ann.
I have a FM book, and inside is a photo of Lindsey sitting and playing guitar in his 'artificial rain room' at home. Could this be a clue?