Daniel DiMaggio wrote :
"Improvised? If so then its amazing - free improv from the 20s."
Between 1750 and 1850, keyboard methods always include
chapters on "fantasizing", which we now called improvisation.
The process of fantasizing followed certain principles, and
a few rules were never far away.
The art of fantasizing, without which a keyboardplayer was not
considered a professional, founds its glory in the
cadenzas which were played in concerti.
This is nothing new in Mozart
(improvisation had been going on for centuries), but the sudden
and complete silence of the orchestra was still something of a
novelty in Mozart's time.
The function of the cadenza is not to imitate the composer, but
rather to give the soloist the opportunity to increase the
excitement by adding his own personal contibution.
In the silent (movie) era, there was (always) a pianoplayer
who was improvising (see also the burlesque movies) :
as viewer,it was common to pay the entrance and the pianoplayer.
Musical accompaniment was provided by a piano during the less
frequented hours, supplanted by a trio who arrived at a fixed time
regardless of what was happening at the screen.
Sometimes a movie was shown in old disused churches
and it's supposedly through this that the employment of an
organ for accompaniment in larger cinemas became general.
(see DVD soundtrack Nosferatu)
See Thomas L.Talley, who built in 1905 a theatre with organ in LA.