Beethoven's Immortal Beloved: The Letter of July 6-7, 1812
The letter is shrouded in mystery: in what year was it written, to which city was it sent (or not sent) and most importantly, to whom was it addressed? There is general agreement about the date (1812), the place (Karlsbad) and that the addressee was a married woman, but the identity of the lady who so captured Beethoven's heart has remained a question mark.
Ibes, Willem (Wim), "Beethoven's Immortal Beloved: The Letter of July 6-7, 1812" (2002). Music Lectures. 3.