[The use of improvisation] makes it impossible for any two players to execute K. 622 the same way, as is, sadly, so often the case today. The tool may be likened to the thing that makes a hockey game interesting: once the puck is thrown down, one has no idea what is going to happen. And that is one of the principal reasons why eighteenth-century musicians improvised: it made every performance of a work measurably different from every other performance of that same work. As such, it was a tool
used to create freshness and originality, the very thing that we all want to have in our performances.
– Daniel N. Leeson, Spontaneous Improvisation in Mozart Performance