Which preposition to use with extemporising

before Occurrences 2%

But when I was presented to Lord Nevil I desired, perhaps too ardently, to please him; I displayed all my talents, dancing, singing, and extemporising before himI believe, though I am not certainthat I appeared to Lord Nevil somewhat too wild; for although he treated me very kindly, yet, when he left my father he said that he thought his son too young for the marriage in question.

in Occurrences 1%

The baron withdrew silently, and returning later found Beethoven extemporising in heavenly mood.

on Occurrences 1%

I stayed till it was time for church, and when I entered it I was met by many a tearful face; papa announced her death from the pulpit, and is going, this afternoon, to throw aside the sermon he intended to preach, and extemporise on "the first Sunday in heaven."

out Occurrences 1%

Upon a small table extemporised out of a candle-box, which stood in the centre, Yagór soon placed two cups of steaming hot tea and a couple of dried fish.

Which preposition to use with  extemporising