I couldn't transcribe all of what Hughes had to say, but he goes on to relate an example of having a young man with a good tenor voice came and sang a few songs for him, including "Down By the Sally Gardens". The singer had learned it from listening to the radio, to an arrangement Hughes himself had done, but Hughes pretended not to know the song at all. The youth sang the song a little differently than the tune that had been recorded, but he remembered Yeats's words perfectly. The singer had created a new variant that matched the words and spirit of the song completely. I think his point is... to just keep singing. The songs will be molded this way and that way, and they will take on a life of their own with the spirit of the singers that sing them.