Which preposition to use with strum

on Occurrences 6%

One, in a short blue skirt, was blowing at something; another in pink drapery (who squinted) was strumming on a lyre; other figures were in white, with their mouths open like young birds preparing to be fed by older birds.

in Occurrences 2%

I awoke shortly after daylight, thinking I heard an aeroplane strumming in the distance, and was drowsily wondering whether or not it was fancy, when a crash echoed up the valley.

at Occurrences 1%

She sat thus for the better part of an hour, motionless except for one forefinger that was, quite unconsciously, tapping out a popular and cheap little air that she had been strumming at the piano the evening before, having bought it down town that same afternoon.

with Occurrences 1%

" "Leon, Leon, won't you sit down if mamma begs you to?" He sat then, strumming with all ten fingers upon his knees.

Which preposition to use with  strum