Dear Onela
This theme could be played on various duduks, my best guess is a duduk in the key of A, because of tones used . But it can also be played with a G duduk or Bb. it depends on how clever the player is,with the halfhole technique, to obtain chromatic notes. But as a standard rule, avoid too many halfholes, because they are difficult to play in the right pitch. Finally it is also difficult to decicde the key, because of the recording studios ability to manipulate the key and sound.
But this can be played with a duduk in A. You can also get help to decide the tones used, by looking into duduk.coms fingering charts, and use a piano or other instrument to play along with the recording.
best regards
Hrimnir
To see all the duduk types:look into duduk comīs fine site about these instruments .