Thank you for that information, Fred. It is interesting that the earliest appearance of the song seems to be a book published in 1968.

I looked at the sample page of music on the link you provided to Ars Musica and it appears to be in a very similar format to the book I mentioned earlier, Sing Care Away, which contains songs often with harmony lines, or songs to be sung as a round. In fact if I had seen that page of music my first thought would be that it came from the same book, except that the lyrics are in German.

It is especially interesting to read that you said, "..a lot of songs originating in the third reich were rebranded and sold to us as folk songs from other countries". I suspect that could explain this song's origins.

I have never heard the Autumn song until I read about it here in this thread. I definitely don't recognise the lyrics.

I have listened again to the melody of the first verse of the early English song Sumer is icumen in and the I still think that the chord progression seems very similar to the Autumn song. The two songs are stuck in my head. I hear first one and then the other.