These are justly famous recordings from the first "complete" survey of the Cantatas using instruments and performing practices from the time the works were written. Nearly forty years on, they still have a freshness and sense of adventure sometimes lacking in some more recent HIPP recordings, and their joy in communicating this Music is palpable. Recorded sound is clear, and if the (disgracefully unnamed) boy soloists are occasionally left short of breath at the ends of long phrasing, this merely gives the recording a greater sense of "live" sponteneity that would be lost on a re-take. And balances are excellent, too.
Caveats? Well, I find Leonhardt's chosen tempo for the first movement of BWV 39 too sluggish; and the choir is larger than the one-voice-per-part approach that I prefer. But these are small "flaws" (and matters of opinion with which others will heartily disagree) in performances that I have repeatedly enjoyed over the years. And at this price, there's no better introduction to these glorious scores!