Question about musical notation (Arvo Pärt-specific?)

Cafe Society
1

I am looking over the sheet music for Arvo Pärt’s Fratres and I’ve noticed some unfamiliar symbols – in this image, they’re the brackets(?) or vertical lines around the notes circled in red. You can see that in the measure before this one, the same notes are indicated without the brackets. I’m also listening to a recording of the piece and I can’t discern anything special about the way the circled notes are played, nor are they played differently from the same notes in the previous measure.

What do the brackets signify and how would I play the notes circled?

I’ve also noticed the brackets in Pärt’s Variations on the Healing of Arinushka, placed around single notes. I’ve been playing the piano since I was 4 and I don’t recall ever seeing this notation before – is it peculiar to Pärt, or is it common and I just haven’t been paying attention? :o

2

Count the beats there. It’s 8, a whole note normally has 4. So it’s a double whole note or breve.

3

Ahh, thank you!

4

Correct. I’ve always thought it was hilarious that the double whole note was called a “breve” (brief) in the breve/minim/crotchet/quaver terminology. (It’s “brief” compared to the longa, which I’ve never actually seen used.)