We hear about the precarious life of a musician dependent on patronage and the whims of the German nobility.  We hear Bach's acerbic wit and cut to his conducting a choir where we realise he is not just a perfectionist, he has low levels of tolerance.  We see he has a bad temper and is stubborn, so will fall out with those he depends on financially and get into petty quarrels.  We also appreciate the humour of Bach's witty lines and put downs.