I was thinking about this and came up with a concept of a diaboli instrument. Diaboli come from a loud smoke filled island, where communications would be difficult. Their traditional instrument would probably double as a communications device, like a signal drum or a bugle. So naturally, I thought a variant bagpipe would make sense. It is also likely to be unpleasant for most people, something that diaboli would like. My concept was of a large instrument made of brass (there being little wood on the island diaboli came from). I thought it would have a drone and two chanters, all of them coiled together and merging to share a single bell. It would also have elaborate valves like a french horn. I would name it a "Diaboli Caller".
I thought it would exist in multiple registers, like a saxaphone (alto, tenor, etc..)
Two more ideas about it:
One is that it could have become a traditional instrument for funerals of the Ochtarcal guards. However only a few diaboli still know the original signaling code. And a bit of diaboli mischief has continued. The traditional guards theme translates to something like "I'm a guard / I don't understand my words / I'm babbling like a fool / because I'm a guard. But only a handful of diaboli musicians and a few scholars would know that.
two is that the traditional way of referring to playing this instrument is to say "I am embracing my foe" in diabolese. This may or may not refer to the original source of leather on the airbags. It may also just mean it's really hard to play the instrument well. The answer is unknown and unprovable.
I would love to give my diaboli character one of these.
Comment if you think there is any value in the idea.
A.K.A. Cirerey