This 2-CD set has first-rate interpretations of Martinu's 5 Piano Concertos and the 1938 Concertino. (For an acceptably good series-in-progress, see my comparative review of the Naxos CD with his Piano Concertos Nos 3 & 5, & the 1938 Concertino by the Bohuslav Martinu Philharmonic Orchestra under Arthur Fagen, Giorgio Koukl on piano.)
As a model or microcosm of this set -- with Jiri Belohlavek with the Czech Philharmonic Orchestra, Emil Leichner at the piano -- I've chosen the closing Allegro of the 1938 Concertino. It is only one of its nine movements, but a representative sample for consider various vital aspects of this music.
The Czechs summon build-ups effectively in this movement, while also developing contemplative passages of great subtlety. The rhythmic core of the music is also far better in hand, through sharper execution, than the Naxos version. Better considered as well is the sound spacing to suit the music's needs. The sound is better adjusted in this Supraphon set, both in shifting instrumental groups for emphasis into the fore or background for emphasis, and in volume dynamics according to the drama.
All of these result in a performance that is full of conviction: strident and razor-sharp where needed, and well-nuanced where sensitivity is required. Belohlavek coaxes colour and ornamentation from the orchestra both to accent and add contour to the soloist's part, rather than acting in alternation with Leichner, the pianist - who ends up not as in the fore as Koukl, on Naxos. Under Belohlavek, his part is closely integrated with the orchestra (the same holds for the timpanist, incidentally, who also stands out much less than on the Naxos).
The Czech Phil's tighter ensemble delivers slow passages of great refinement while also managing robust, hair-raising fortissimo execution when that's called for. This last is done with jazzy flair on the trumpets' climactic entry (at 5:10): the players are all but seen to rise and blast out their brief part with dizzy exuberance. Closer attention to the shape of what remains after this peak also brings out some more tightly-wound, eventful music -- just listen to those lovely, long pizzicato lines of cellos and double basses shaping the closing passages, leaving no sense of disappointment when the end arrives.
You might also want to consider Bohuslav Martinu: Piano Concertos Nos. 2, 3 & 4 with Rudolf Firkusny on piano and Libor Pesek conducting the Czech Philharmonic Orchestra.
Still, for a complete set of these concertos this 2-CD album with Belohlavek conducting and Leichner on piano is unsurpassed. If you're considering which set to get, this is the one!