Master the music: memorizing all those songs
Indeed — how does one memorize 577 songs? Many years ago I came across a book entitled "How to conquer stage fright" written a long time ago (I expect it's out of print.) One of it's main tenets was the idea that you could memorize a piece of music without actually singing or playing it, by way of preliminary visualization. I applied that principal to the organ repertoire I was then studying, with phenomenal results. Of course I felt nervous before the performance (an internal exam in the Hochschule in Freiburg), but while playing I was able to listen, really listen, in a way I could not when using a score. And that white-hot concentration on the matter in hand banishes nerves, as far as I'm concerned.
When it comes to vocal musice (I no longer play the organ), my method is as follows: I first of all memorize the poem in question mentally, returning to it day after day, adding line after line, verse after verse.* Then I recite it until I feel I could "perform" it in public. Only then do I turn to the music, applying the same "layering" procedure", until I can mentally perform the entire piece. (Here a good knowledge of harmony is indispensable.) Once that can be done securely, I record the accompaniment, and begin to sing, phrase to phrase, (never too much in one day) and once that process is complete I let the song lie for a certain time, rather as one would let cheese ripen in a cellar. The final stage is the fun part: working with Michel Stas. In general we rehearse 8 to 10 times before a performance: first a read-through, then each song in detail, then one or two dry-runs.
All of this is extremely labour-intensive — each recital programme takes three months to prepare. Many musicians I know would cavil at this, but I can only say for myself that I feel completely free to express myself and serve the music. Master the music, or the music will master you. It works for me.
*Rereading this three years later, I see that my technique has evolved somewhat. The visualization process is just that, but one does actually need to sing the song in order to memorize it! As part of that process, I now record the songs at the piano, playing a dumbed-down version of the accompaniment together with the vocal line. I never listen to commercial recordings until after the whole process is completed.