Joshua Rifkin and the Bach Ensemble have produced the most important recordings of Bach cantatas in the last 20 years, give or take. In 1986, the idea that Bach did not use choirs to sing his choruses, but gave that task to the singers also used as soloists so that each part in the chorale movements are sung by one voice, was controversial. Since then, however, Rifkin seems to have been vindicated, and modified versions of Rifkin's theory have been utilized in performances by, not only Rifkin the Bach Ensemble, but also by others including Andrew Parrot (who wrote a book about it) and Ton Koopman.
The resulting sound from performances where the OVPP method is engaged is radically different from that on full-chorus performances. For one thing, voices are allowed a great deal more room for individual expression - ornaments, dynamics, when to use their vibrato's and when not to. Additionally, choirs have a full, uniform ripeness of sound, that has never seemed quite right in the cantatas (as opposed to the St. Matthew Passion for example). The harmony and counterpoint on most of the cantatas, as well as the precision of musical ideas and the extremely limited instrumental parts - in many movements, there is nothing more than an oboe or a pair of recorders plus continuo - belie an intimacy that big choirs and orchestras (or even little choirs and orchestras) cannot capture by definition.
Included here are six works, including cantata number 106, "Actus tragicus", which is one of Bach's most profound works and three cantatas for bass solo. including the well-known "Ich habe genung." For these three alone, this recording would be indispensible. As it is, the six cantatas recorded here seem not only deeply beautiful, they are definitive. I will never hear 106 again without comparison to Rifkin's. Ditto the bass cantatas. It's hard to imagine anyone more suited than Jan Opalach to sing the bass parts of these works.
Rifkin's first recording of six "favorite" cantatas was problematic for many listeners because of a number of problems. The singing was excellent in places and not so in others. The sound engineering was generally no asset. But that CD set remains indispensible. Most of the sound and all of the singing issues are resolved here. I recommend following along with the texts at first so as to "get" Bach's allusions and compositional technique for each work. Once you become familiar, though, what a joy it is just to close your eyes and be transported to the land of "the persistent sublime."