There's a really strange sounding instrument, similar to the one you once heard at school aged about seven in your very first music lesson. The only noise one can compare it to is the sound of horse hooves galloping. After using the Googles I believe them to be Krakebs. You hear them in the below Pulcinella Ballet performance by Stravinsky at 11:41.
My question, however, is why was this not included in his original rehearsal for the piece? I mean in all fairness you would have to be a very brave man or woman to mess with a composers work of Igor's stature.
His original rehearsal is here, no horses though? :-) You can hear the same phrase below at 2:09.
Is it commonplace to add further instrumentation to an already published composers work?