Naemanson, we have talked about the twin thing some. Perhaps you will understand when I say that I should preface this by saying that I am wired for twinship, so I really should be working in partnership for the song process to work well for me. But what I am going to describe is how I do it alone. (You'll see though that in a sense I am the two partners. But I would rather have a real partner.)
A phrase will pop into my head and then announce, "I'm a song, let's make me!" And I go with it. It often happens now when I am writing to or thinking about someone, and a lyrical frame of mind will come over me, a romantic view of the world as I catch a moment of it to savor...
A tune will come for it once I wonder how it would sound.
Tunes by themselves, now, usually come in the car, unbidden, and a melodic phrase will start that off and I'll whistle it or hum it and then it starts to go into variations and developments. Once I realize that is happening I usually worry for a moment that I won't remember it, so I decide nowadays to go through it again listening as if to a record so I can "learn" it. But usually if it was a good one it comes back a few days later all by itself, while in between I can't remember it at all even if I did learn it.
Very rarely the words and tune come together, whole. The Elian song was like that, and so was the Sugar Dog song.
Once they start to come it is a lot like prayer often is for me. A thing will start and I will take it a phrase at a time, listening for what is coming next, and enjoying the delightful surprise that comes. Sometimes I think I know what the next phrase ought to be but if I really listen, it's somehting else, and much better than what I might have expected.
Also sometimes words will come, especially if it's a funny song, as I sing them.... there was an hour one day of new verses to Swing Low Sweet Chariot that, as Matt would say, ROOLED. (I was driving.) But they didn't stick. I'd have to have it happen again, fresh. Sometimes these words are so well crafted I realize how dumb it is not to have a tape recorder in the car or in my purse, but then I forget the purse, so....
Anyway, these words often form the motivation to come home and write, but when I do, it's usually not the words I first had, at all... the sentiment will be there, and maybe the opening phrase, but then I have to make it up all over again, and they seldom seem as good as what first came.
I just let it come as is. Then, whatever the genesis, once it's out there on paper or, if a tune, in my head to keep, then there is some editing. Or for a tune I may make myself create a bridge if the verses sound too repetitious to me.
And many of these would be best sung by someone else, but I don't know who I am writing them for. Dharmabum and I have talked about some duetting; maybe they are his.