Technology is an amazing thing. This is a nice performance of Mozart, but no human beings were involved: computers read the sheet music, played the piece, imitated the piano, and provided the ambiance. You can hear some glitches near the end; I think the computer's page-turner was slow.
The producer says, "I bought a copy of the sheet music for this piece then input the notes into Sibelius. A MIDI file was then exported from Sibelius and imported into Reason. From there I added a couple of effects and tweaked the MIDI data a little bit. The pics are scanned copies of the sheet music set to a transparent Mozart background."