von Bulow?
If so, here's the next one...
In his General History of Music, Charles Burney describes this lesser-known English organist-composer as follows:
It seems necessary to give some account of this musician, who was an enthusiastic, ingenious, and worthy man, of considerable eminence in his youth for his performance on the harpsichord and organ, both as a sight’s-man and voluntary player; and his intellects being a little deranged in the latter part of his life, rendered him so whimsical and eccentric a character, that he is too prominent to be over-looked.
Who is the mystery composer?
HINT: He was largely responsible for Domenico Scarlatti's fame in England