I rather like this reviewer's take on this question: "Consider: A professionally competent 18th-century burgher raised a very large family, came and went as a busy and productive musical technician, associated himself for nearly three decades with a church in Leipzig whose school of 55 boys he taught music while also training a choir. He provided his employers with the cantatas they required for Sundays and feast days and was active in the civic musical collegium. He traveled, though sparingly, and spent tedious hours copying out his own material. He was disputatious about a lot of things but was finally submissive to the requisite councilors, dukes and princes. When the end came, he left behind, in the city of 32,000 souls, a huge family, an indigent widow and a library of compositions which would ordain him as the greatest musical artist who ever lived."
So what happened here? The author provides all sorts of interesting information, but I guess there's no figuring out how Bach did it. Bach was anything but the lonely-genius-artist - he was an engaged family man with a demanding day job.
As I get older, I spend more and more time with Bach's music. And I'm pretty sure the greatest concert I've ever attended was this presentation of the B minor mass). (Interesting to read that Beethoven bought his own copy of this work a century after it was written.)
The last portion of the book focused on technical details - for me, sort of like reading a foreign language - I just don't anything about composition or theory.
I'm pretty sure I need to attend a Bach concert at this church in Leipzig.
Two and Three-Part Inventions
Well-Tempered Clavier
French Suites
Goldberg Variations
The Musical Offering
The Art of Fugue
Cantatas, Motets, etc. (thankful for youtube access)
Brandenburg Concerto
St. Matthew Passion
St. John Passion
B minor Mass
Etc.
Etc.