Why Is The Flute a Woodwind?

It might seem strange that the flute is a woodwind instrument, given that flutes are typically made out of a metal such as nickel or silver as opposed to wood. So, why is the flute a woodwind instrument?

Flutes are considered woodwind instruments because instruments are classified on the basis of how they produce sound and are played, not based on the material that they are made out of. Woodwind instruments produce sound by splitting the air blown by the musician against an edge (i.e. the lip plate of a flute or the edge of a reed), whereas brass instruments merely amplify the sound produced by the musician’s vibrating lips.

We’re going to address the full set of criteria which goes into determining the flute’s status as a woodwind, and show you why the material that it’s made out of isn’t sufficient to change its classification.

Criteria #1: The way that the instrument produces sound

This is the primary criteria which determines whether an instrument falls into the woodwind or brass families. Virtually all brass instruments produce sound in the exact same way: the musician vibrates their lips (this is called buzzing) and that vibration is then amplified and altered by the instrument. Notably, the flute does not produce sound in that way, and this fact already excludes it from being classified as a brass instrument.

There are several different ways in which woodwind instruments can produce sound. Most commonly, woodwind instruments have a reed which produces the sound of the instrument by vibrating as air moves past it. A reed is a small piece of cane (or sometimes plastic, due to modern developments) which is placed on the mouthpiece of a woodwind instrument. Saxophones, clarinets, bassoons, and oboes all use reeds, and hence are classified as woodwinds. 

Flutes do not use a reed, and you might intuitively think that this fact would exclude them from the woodwind family as well. However, flutes still use an acoustic principle which is similar to the concept of a reed. Specifically, flutes produce sound by splitting the air blown by the musician across a sharp edge (that is, the lip plate of the flute), and causing the air inside the flute to vibrate. 

Similarly, the vibration of the reed alternates between opening and closing the aperture of the mouthpiece, which ultimately also causes the air inside the instrument to vibrate. In both cases, the sound is produced by a part of the instrument, not the musician.

The important difference here is that woodwind instruments use the air blown by the musician to produce sound in some way. The musician might blow the air, but ultimately it is the instrument which produces the sound. Brass instruments, on the other hand, merely serve to direct and amplify the sound which has already been produced by the buzzing of the musician’s lips. 

Given that flutes produce sound by splitting the airstream of the musician (that is, the instrument itself is actively producing the sound), it should be clear that flutes fall into the class of woodwind instruments, not brass.

Criteria #2: How the instrument changes pitch

In general, woodwind instruments have keys. Keys are buttons on the instrument which can be pressed to either open or close a hole on the body of the instrument. Pressing a key either allows or prevents air from escaping at some point on the instrument, which either raises or lowers the pitch. When the musician presses down additional keys, the flow of air can no longer escape in the same place and is forced to go through a longer portion of instrument, lowering the pitch.

Brass instruments, on the other hand, usually change pitch through the use of valves. A valve is a mechanism which, when pressed, re-routes the air to a longer length of tube. Note that in the case of brass instruments, the sound always escapes the instrument in the same place (that is, the bell). Rather than creating an opening for the air to escape at a different point, brass instruments simply alter the length of tubing that the sound goes through before it reaches the bell. 

Not all brass instruments use valves. Some, like the trombone, instead use a slide. Slides operate by a similar principle as valves. The musician simply adjusts the position of the slide to lengthen or shorten the amount of tubing that the air goes through before it reaches the bell. As is the case with all brass instruments, the air still reaches the bell before the sound is released, as opposed to woodwind instruments where the point that the air is released is altered through the use of keys. 

The key takeaway is that a woodwind instrument will have multiple areas where the sound can escape the instrument, whereas a brass instrument will only have one. 

Once again, this criteria demonstrates that flutes fall into the category of woodwind instruments. Flutes have keys which open or close holes, allowing the air to escape the instrument without going through its full length. Only on the flute’s lowest notes will the air reach the end of the instrument; most of the time the air will escape through the holes closest to the head joint.

Criteria #3: Whether or not the sound of the instrument has a specific direction

Typically, the sound of a brass instrument is pointed in one specific direction, while the sound of a woodwind instrument goes in every direction. This makes intuitive sense; since all the sound of a brass instrument is released at the bell, all the sound travels in the same general direction.

In the case of woodwind instruments, the keys allow sound to escape at various points of the instrument. The sound travels in no particular direction because it is going in every direction. 

Again, we can see that the flute fits in with other woodwind instruments, rather than brass. Since the flute has keys like every other woodwind instrument, the sound often escapes well before it reaches the bell, and goes in no particular direction.

Is the material that an instrument is made out of a determining factor in how it is classified?

The material that an instrument is made out of has nothing to do with the way that it is classified. Woodwind instruments can be made out of metal, plastic, wood, or other materials. Brass instruments, while commonly made of brass, can also be made out of plastic.

The reason that the terms “woodwind” and “brass” were originally coined is because at one point the material of an instrument did matter. Clarinets and flutes were originally made out of wood, and even the first models of the saxophone were constructed from wood. 

However, as instrument makers gained access to manufacturing and plastic, many of them began to experiment making instruments in their traditional designs but with other materials. The sheer diversity of materials that can be used in the production of instruments effectively makes the use of a material-based criteria obsolete. Even with different materials, the designs of the instruments (and the need to classify them into separate categories), remains the same.

Is it ever ambiguous whether an instrument is woodwind or brass?

In general, all the criteria which make an instrument woodwind tend to go together. There is no instrument, for instance, which produces sound the way that a woodwind instrument does, but changes pitch the way that a brass instrument does. The same is true vice-versa; if an instrument fits some of the above mentioned criteria of a brass instrument, it will almost certainly fit the others as well. 

Some instruments that combine the characteristics of woodwind and brass instruments have been attempted in the past. However, they’ve almost always been failures. For instance, there used to be such a thing as a “keyed trumpet,” which produces sound the same way that a brass instrument does but changes pitch the way that a woodwind instrument does. However, it was not acoustically functional.

So, it is not usually ambiguous whether or not an instrument is woodwind or brass, since there is rarely ever overlap. In the case of the flute, it fits every criteria of a woodwind instrument even though it is often made out of metal.