Dmurfet et al., Despite all the talk here about the cantatas, the Bach work I would recommend here would be the B Minor Mass, one of Bach's greatest works (none of the unevenness and pedestrian level of inspiration that impairs many of the cantatas) and one of the greatest choral works ever written by anyone. It's hard for me to believe that anyone with ears and taste could listen to a good performance of this heaven-storming piece of music and remain unmoved.