Fark:
Dark? You find the Requiem dark? I think it's glorious and celebration of life. (Although, if it's fire you're after, try the 35th Symphony, the so-called Hafner.)
Mozart might have faded into oblivion if not for his wife. She really did lock up his writings, as shown in the movie. They had two sons, not the one, however. Shortly after his death, she remarried and together with her new husband, they worked hard at marketing Mozart's music. Made more of a living from it then Mozart ever earned during his brief life-time.
Mozart's sister (can't remember her name), was also a talented musician and composer, but because she was born female, whatever she wrote or did passed into feminine obscurity.
Was it Felix Mendelssohn who was responsible for ressurecting Bach's music?