John Landecker sent me this yesterday and asked me what in the world it meant...
I explained it to him this way. Landeck is a town in Austria. Someone from there is called a Landecker. Every year they stage an Advent festival, a sort of Christmasmarkt like they have in Daley Plaza in Chicago. At the festival in Landeck, they sing Christmas (or Advent) songs. So...Landecker Adventsingen literally means "singing at the Landeck Advent festival"
German is a very literal language