New music vs improvisation

I went to a concert lately
where an organist played modern-sounding piece
among many other compositions.

As I was listening to these harsh sounds,
I tried to observe my reaction to the music.
​
Since I didn't know the piece,
it might have been an improvisation just as well.
In fact, I started wondering,
what would have happened,
if the organist could have improvised something similar
instead of playing previously written out composition
which nobody in the room knew.

That's a risky thing, isn't it -
if you play what's written by somebody else,
you feel safe
because the composer took all the responsibility.
But if you decide to improvise,
​you are on your own.

What would you choose - 
to play an unfamiliar modern organ piece or
​to improvise something in a similar style?

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Ausra's Harmony Exercise:
Modulation from A Major to B minor: I-V43-I=IV/iv-iv6-ii43+-i64-V-V7-i-iv64-i

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