There seems to be a huge variety of ways to play the introduction to this. I take this as a genuinely alla-breve Andante and therefore not all that slowly at all. I don't think this is Moonlight Sonata territory. Andante is not really very slow, and alla-breve gives us just two beats per bar (one per six notes). It seems that many editions published the introduction as being in 4/4 and not 2/2 from the mid-19th century until well into the later 20th century, perhaps accounting for how slowly and searchingly some pianists have played it, and how the musical tradition has been laid down. For sure you can "find" that expression in it... I'm just not sure it is really intended. The work was unfinished in autograph and there is no direct line to how Mozart payed or taught it.
(A tiny bit of interpretative reasoning in addition...... I had for a while found this piece difficult to bring off as a unified whole; as it is too easy to make the first minor-key part so weighty and searching that the final D major section simply doesn't fit, unless you try to get that section to carry some kind of extra profundity which I'm afraid I just don't see in the notes. A swifter tempo for the introduction, and a very improvisatory main-section [and not indulging in much weltschmerzigkeit] feels - to me - to be a way to balance the work properly.)
11 май 2020