J.S. Bach's Adagissimo

[thecrow]

Hi, I'm in the process of learning J.S. Bach's Adagissimo (BWV 992) and I'm trying to learn more about the story behind this work but I'm having difficulty finding information on the internet (I also searched this forum). I am actually finding conflicting information (lament for a brother, lament for friends, brother going off to war, brother going off to study the oboe). Does anyone have a realiable sorce of information (website, book, personal experience and/or knowledge ...)? I absolutely fell in love with this piece of music and I want to make sure I understand why Bach composed this! Any help would be greatly appreciated - thanks.