From the artist:
A harp is built around string length, with strings shortening as they ascend in pitch. This piece behaves like an impossible harp, as strings morph to the needed lengths.
It is interactive as well, though I am pretty certain I cannot improve upon Bach.
And if you’d like to hear Yo-Yo Ma play this particular cello concerto, watch any movie ever, or any “heart-warming” movie trailer. (Its ubiquity in no way diminishes its majesty.)