Bone flute questions

[Noumides]

I saw a player using a bone flute in the game. I google it and I red, that a bone flute is obtainable with a key, that can be found on original soundtrack cd case.

I see 4 bone flutes in the game store.

a) Asuming one of them is the "soundtrack" bone flute, the other 3 are obtainable by loot drops?

b) If yes which boss are dropping those flutes?

c) which one of the 4 bone flute in the game store is the one, that is obtainable with a key, that can be found on original soundtrack cd case?

[avexy]

You will get one by doing the Yun quest chain in khitai. A quest in Pai Kang will give it to you (you need to be rank 3)

[Kurt2013]

As Avexy said, that is the only bone flute available through playing. The ones you mentioned came with a soundtrack CD to be unlocked in game. Then there are the ones you can buy via the shop.
Different flute names play different tunes as well (slight variations of the same theme though).