Hi Guys: Ken I understand your frustration with regard to the precision of a group in its performance of pieces like the Brandenburgs. However the practice of the day was for the harpsichord to improvise at certain places in the piece. If you listen to two or three recordings of just one concerto you will here many differences in the outcome. That's why I have about four recordings of these concerti. John's suggestion for the Bach will be period performances. Those groups sound very different from those who use modern instruments. That too is an issue at least for me as I prefer the modern. Ironically my favorite rendition as of now is from a period group based in Berlin.
If you aren't happy with your Bach try the tried and true favorite on a Decca twofer and conducted by Benjamin Britten. You can find it on Amazon here:http://www.amazon.com/Bach-Brandenburg-Concertos-Britten-ECO/dp/B00000425M/ref=sr_1_5?s=music&ie=UTF8&qid=1299740548&sr=1-5
