it's not an instrument but a technique
the melody is played with a harmony in scale tone 4ths
e.g.
your melody is
C-D-E-D-C-A-G-A-C-
scale tone 4ths would be either
F-G-A-G-F-D-C-D-F played above it
or
G-A-B-A-G-E-D-E-G played below it
if you are interested in teh sound used in that spot it is a pair of end blown flutes similar to the Japanese shakuhachi or Peruvian quena