Does a flute's bore need to have a circular cross-section?

January 29, 2019 2:20 PM

Is there a reason aside from ease of production why flutes have circular bores? When making PVC Irish flutes, could one squish the distal end, reducing it's cross-sectional area and effectively creating a conical bore like recorders have and bringing the second octave into tune?

I'd especially appreciate if anyone has practical experience experimenting like this (or in other ways!) with homemade PVC flutes.

posted by starfishprime to Grab Bag (9 answers total)

I can't think of any reason based on acoustics and resonant modes of a cylinder vs a cone.

Lots and lots of instruments exist in circular and conical bore varieties. In fact, Wikipedia's article on bores tantalizingly indicates that some flutes "(pre-Boehm)" had conical bores. Sadly, the Wikipedia page for flutes currently has no relevant occurrence of the word "bore".

Interesting question, consider posting on MetaProjects if you end up making a conical flute!
posted by SaltySalticid at 3:58 PM on January 29, 2019

Some professional instruments have had a conical bore. Maybe piccolos, especially. But I doubt there was much of a taper.
posted by SemiSalt at 4:13 PM on January 29, 2019

As I understand it, (I'm only a drummer :) ) it's the volume of air that matters... so, as long as the cross-sectional area's the same (major axis^2 + minor axis^2) = r^2 I reckon it'd still work/be in tune (for the same length tube). How it handles and how easy it is to play may be another matter (not to mention embouchure etc)
posted by Dub at 5:32 PM on January 29, 2019

Rick Wilson's page on 19th century Boehm flutes discusses Boehm's 1832 conical flutes (made of wood) and his 1847 cylindrical flutes (made of metal).

Wilson notes some acoustic differences:

When the cylindrical Boehm flute was introduced in 1847, it was often adopted quickly by those already playing the conical Boehm flute. But conical Boehm flutes continued to be made and played, since some preferred their tone. The conical flute tends to have a sweeter and softer sound.

...

Leonardo De Lorenzo reports that on a visit to Munich in 1926 he "...was greatly surprised to learn that [Gustav Kaleve, a successor of Tillmetz], and in fact, most of the flute players in Munich, use the conical flute. They considered it more suitable and better adapted to chamber music, as it more nearly approached the flute for which the music was written." De Lorenzo relates that he personally did not agree with this.

For his part, Wilson claims that "[the cylindrical bore flute] tends to be much richer, especially in the low notes, than the conical bore flute."

Wilson also notes at least one practical difference: "The tone holes could be made larger on a cylinder (the tone holes on a conical body could not be larger than the bore), so large that they could not easily be covered by thin fingers." This led to the use of key cups and pads for all holes instead of ring keys.
posted by jedicus at 9:45 AM on January 30, 2019 [3 favorites]

Response by poster: Thanks for the infos so far. Does anyone know of flutes with NON-CIRCULAR cross-sections. For example, ellipses. Cylinders and cones both have circular cross-sections.
posted by starfishprime at 11:46 AM on January 31, 2019

Kazoo? Ocarina?

I think some organ pipes are rectangular boxes, or at least have parts that are. A musician I know called a pipe organ "a ccollectlon of flutes".
posted by SemiSalt at 9:58 AM on February 2, 2019 [1 favorite]

As a terminological note: neither cones nor cylinders need have circular cross sections in the geometric sense of the words. In common English, when we say cone, most people think of a right circular cone, like a traffic cone. But an oblique rectangular cone is still a cone.

And I’m not sure how it would work for a flute, but some loudspeaker systems feature oblique rectangular cones, and it would seem their acoustics are desirable in at least some circumstances.
posted by SaltySalticid at 11:02 AM on February 2, 2019

I think the OP has the answer: the shape of the instrument doesn't matter much except maybe to the ear of a fine musician.

However, I came for the benefit of instrument nerds to point out that I happened on an advertisement for a conical flute. It's on the website of the Wichita Band Instrument Company.

It's an ebony/ivory flute made before 1830 by Baumann. Yours for only $6850. Picture.
posted by SemiSalt at 11:55 AM on February 2, 2019

Response by poster: I found a youtube video showing a flute with a bore with a square cross-section, so I'll consider it confirmed that one can shape a flute's bore how one wants and they are only made circular for logistical reasons.

Here is a link to that video.
posted by starfishprime at 7:44 AM on February 4, 2019 [1 favorite]