More then most like your Duduk is in A. A Major (A, B, C#, D, E, F#, G#, A). The starting note though is actually the 6th degree of the scale, so with all 8 finger holes and the thumb closed, it is actually an F#, then it goes up the scale. The range of the Duduk is about an Octave and a fourth (so that means it goes from a lower F# to a higher F#, and then up to a B (which is a fourth if you think of F# as being one). If you have a good reed and good technique you can play a C note, but it’s very difficult to do, and is usually used as a grace note, not a note to be held for long or to sustain as part of a melody.