I have been trying to play a piano piece in 12/8 time, and I am getting stuck in this one measure. I keep counting the beats in it, and I always come up with 13. In the measure are these two brackets with 2’s over them each, above two quarter notes each, one bracket per clef. Do they modify the number of beats for the two quarter notes below the brackets? Do these make the measure 12 beats, somehow? Are they like triplets? Perhaps they relate to the tenútos?
It's a duplet. I expect you are familiar with triplets, where three notes fill the time normally taken by two. Well, this is sort of the opposite! We're in 12/8 time, the beat is a dotted quarter, and this is two quarters filling one beat - the time normally taken by three 8ths. The length of the bar is still the same, the beat is still the same.