As near perfection in balance of sound, of the integration of piano and orchestra, of the timing of the entries of ensembles and of individual players, as you may find in a lifetime of listening. The recording engineers and the conductor, Claudio Abbado, did a grand job.
As for the pianist, Maria João Pires, her contribution is precise, joyful, light-stepping, apt to delight the hearer throughout the two CDs. Three of the cadenze are by Serkin (one each for the first and the final movements of concerto No. 21) and by Badura-Skoda (for the first movement of concerto No. 26). These are witty and apt. The others are by Mozart.
Four of his concerti - Nos. 14, 17, 21 and 26 - are captured here from different occasions (two of them at live performances) over the period 1990-93 and with various producers and engineers. Even so, all meet the highest standards, all are marvellous evocations of Mozart, the dancer as composer, applying his inventiveness during the zenith of the Enlightenment.
Two different orchestras were at work - the Vienna Philharmonic for 14 and 26, the Chamber Orchestra of Europe for 17 and 21. Each is dictinctive, the former band perhaps a tad more weighty and rich in the string section, the Chamber outfit a little less rooted in the grand tradition of interpretations by long-established orchestras - but maestro Abbado kept both purring, bouncing, authoritative and responsive to his every cue.
If you can't get the accompanying booklet out of the over-protective CD case, do not fret. You are not missing much. The essay therein is thin gruel.