No, what makes this collection unusual is the instrument itself. Most of the recordings of this music are done with a modern piano. A significant percentage use a fortepiano of the era. This is one of a very few to use a harpsichord.
It's not an entirely inauthentic choice. The earliest works here -- the K 19d sonata, the K381 sonata, and the k358 sonata -- were all composed between 1765 and 1774. It was a time of transition when the use of the fortepiano became widespread. It's conceivable that there were plenty of places (maybe even somewhere Wolfgang and Nannerl performed) where the upgrade from the harpsichord to the fortepiano hadn't been made.
But by the time the Andante con Variazioni in G major, K501 (1786) was written, the fortepiano would have been the norm, rather than the exception in most venues. And the Fantasia in F minor, K608 was originally written for mechanical organ, and later arranged for piano four hands -- well after the heyday of the harpsichord.
That's my quibble with this album, but of greater importance than instrumental choice is the sound. And that's where Basilio Timparano and Rossella Policardo excel. The harpsichord doesn't have the subtle dynamic options of a piano (or even a fortepiano), but the changes in texture serve that function. Four hands playing chords on the instrument sound much louder than two hands playing single lines. And it works.
These are crisp, clean performances that are full of Mozartean energy and good spirits. The harpsichord is particularly effective in the fugal section of the Fantasia, making it easy to hear the individual lines as they interact with each other.
Timparano and Policardo also play expressively, with phrasing and minor variations in tempo that make these engaging performances. I was a little skeptical when I first got this disc. But after hearing it, I'm won over. In the end, it didn't matter to me if Mozart had originally performed all these works at the harpsichord or not. They just sounded right.
Wolfgang Amadeus Mozart: Music for harpsichord four hands
Basilio Timparano, Rossella Policardo, harpsichord
Sonata in D major, K381; Andante con Variazioni in G major, K501; Sonata in C major, K 19d; Fantasia in F minor, K608; Sonata in B-flat major, K358
Stradivarius STR 37045