"Bevelled" is of course the literal translation, but I've never heard of a bevelled wind instrument and I can't find any genuine English references to this term.

This is tricky, because as far as I can see your text is actually incorrect. The Spanish Wikipedia article on the quena says "La quena (en quechua: qina) es un instrumento de viento de bisel".
http://es.wikipedia.org/wiki/Quena
And this seems to be where the reference in your text comes from. But I don't think it's true.

An "aerófono de bisel" (aerophone is a technical term for a wind instrument) is a fipple flute or fipple aerophone. Here's an article on the subject, which clearly illustrates the nature of the "bisel" type of mouthpiece:
https://organologia-grupo2.wikispaces.com/Aerófonos de bisel

It's a family that includes the recorder, the flute, the tin whistle and the ocarina, among others. Here's an explanation of the fipple, and you'll see it's the same thing:
http://en.wikipedia.org/wiki/Fipple

This type of instrument is also known as a duct flute.

But a quena (or kena) is not a fipple flute. It has a mouthpiece consisting simply of an oblique cut and a notch. It's a ductless flute.

"2. Vertical tubular flute with ductless notched mouthpiece. Single-tubed (open distal end), ductless (with a notch for a mouthpiece; the player focuses the air stream directly upon the sound-producing edge in the shape of a notch), vertically or diagonally held, end-blown, with finger holes. Some examples are the Bolivian and Peruvian kena (quena) [...]"
Dale A. Olsen, World Flutelore: Folktales, Myths, and Other Stories of Magical Flute Power, 5
https://books.google.es/books?id=3bUPBAAAQBAJ&pg=PA5&lpg=PA5...

So the correct translation of "de bisel" would be duct or fipple, but this would be untrue as a description of a quena, so I would advise you to put "ductless", with or without "notched".

--------------------------------------------------
Note added at 50 mins (2015-04-17 00:07:26 GMT)
--------------------------------------------------

By the way, the recorder (flauta dulce in Spanish) is called a flauta de bisel in European Portuguese. The recorder is the classic fipple flute and is radically different from a quena, as I've said.

--------------------------------------------------
Note added at 1 hr (2015-04-17 00:18:16 GMT)
--------------------------------------------------

I have found one English reference to a "bevelled flute" in a respectable English source, but it's about a prehistoric flute from Geißenklösterle and I think it's a literal translation of "abgeschrägte" in German (as in the source Natalia has cited).
https://books.google.es/books?id=dHbqAgAAQBAJ&pg=PA49&lpg=PA...

"Bevelled" is not used in any English manual on wind instruments.

--------------------------------------------------
Note added at 1 hr (2015-04-17 01:07:02 GMT)
--------------------------------------------------

A further reference to show what "bisel" means in Spanish in this context:

"Se dice que un instrumento musical vibra por bisel, cuando su sonido es generado por la vibración del aire expelido o insuflado al chocar éste contra un borde rígido afilado o pieza denominada bisel."
http://es.wikipedia.org/wiki/Bisel_(música)