I wrote about this earlier, when I was describing the whole set. This is one part. I bought it later, because I discovered that one of the records of my set was missing. It has four records, but one of them double. So this was meant as a replacement. Of course I couldn’t part with the one in the set, so I decided to keep both.
Wagner originally had the idea to write an opera he called Siegfried. The idea of this all German hero consumed him so much, he worked most of his life on the story. He also named his son Siegfried. When the story proved to be too long for one opera, he split it in three pieces, with an added introduction. This middle part of the cycle remained the core of the story though.