Just noticed, the Berliner Barock Solisten are releasing a new recording of the Capriccio No. 3, along with some Telemann orchestral works, by on the Phil.harmonie label.
For those interested, not on period instruments, despite the rather misleading blurb on the Berliner Barock Soloists' website.
Texture is so important for both Telemann and Zelenka that their music really only works on period instruments. Or, pehaps it is better to say, one loses a lot in their music if not played with the particular colours and textures of period instruments.
It's a very important point that you have raised, as, like you, I much prefer Zelenka on period instruments - provided that they are well played! In many ways, however, "period" and "modern" practices have come together in recent years and the former dogmatisms have declined. Players can now cross the boundaries, not only in style, but also on the instruments themselves.
I agree about the ambiguity of much of this group's publicity. I now have the disc in question and the notes refer to the musicians playing on "historic, though modernised instruments using bows from various periods..." This could equally refer to Heifetz and his Strad. The group photo is also unhelpful.
On the other hand, the portrait of Radek Baborák just about shows a horn with a crook and Google reveals his experience on the baroque instrument. Google equally shows the solo violinist in the group to be expert on the baroque violin and, especially, the director of the sessions to be a baroque specialist. However the second horn, Andrej Žust, is not shown as having any such expertise.
The proof of the pudding is in the hearing, of course. The strings to my ears have minimal vibrato but don't seem as sweet as some of the best period players.The wind players are lively but I don't hear the rich woody bassoon tone that I associate with the best period exponents. The horns are rich, accurate and lack a brassy edge; they are not however fruity, and I will accept that they are not valved instruments.
Tempi are fast, most especially in the Allemande, which is taken at twice the speed of Suk, Bern or Sonnentheil. This of course changes the character entirely and the performance seems not to have been heard by the writer of the notes, who refers to Hypocondrie and "violent vapours of black bile...... transience and futility." Even if these things can be attributed to the music as presented in the other versions, they are certainly not present here!