Lotte Lehmann (1888 – 1976) wrote a number of books on the subject of Lieder interpretation, an art in which she was for many the undisputed master. I remember several books sitting on my school library's shelves. In my collection is only Eighteen Song Cycles, a volume the covers all the important German cycles, or at least those she might have been expected to sing. Mahler's Kindertotenlieder does not appear.
She moves on to cover a few French cycles, including Berlioz' Les nuits d'été and Ravel's Shéhérazade. She includes both piano cycles and orchestra cycles.
Her books fell out of favor, were considered far too specific in their directions. She talks about where your eyes should be directed, e.g.
I took classes in Lieder interpretation at IU and felt that the more specific the discussion the more helpful it was to the singer. Lehmann's best words may lie at the beginning:
"First and foremost I want to say that this book will fail in its purpose, if the young singers, for whom I am writing it, should consider my conceptions as something final and try to imitate them instead of developing their own interpretations which should spring with originality and vitality from within themselves.
"What I want to try to explain here is not any final interpretation, but an approach which may be an aid towards the development of your individual conceptions. I want to point a way which might lead from the lack of understanding of those singers, who seem to consider only voice quality and smooth technique, to the boundless world of expression. And it will be seen that there is not just one, but an infinitely varied pattern of ways, which lead to this goal. Only he who seeks it with his whole heart will find his own approach to interpretation."
I couldn't agree more. Perhaps her books still sit on a library shelf somewhere. See if you can find them.
This is a funny comment I know, but here goes--I think perhaps the stricture against imitation does not really apply to Italian opera. Your heart must still be fully engaged, but the proper style can only be achieved through imitation.
This is the only film of Lehmann singing during her active career. She was 60.