One of the great cries of madness. When Randall Scarlatta did a Schubert set in 2002 with the Seattle Chamber Music Society, he wasn't sure that this was a good song with which to end the set. I told him it was perfect because it so clearly points the way to Wagner. Had Schubert lived long enough to hear "Tristan", I don't think he would have been all that shocked.
I'm curious as to where and how the Lied as a form started. In form, and structure, and execution, it is so different from the chanson and madrigal with which I am more familiar (I am firmly backward-looking. Mahler is an anomaly.)