How ocarinas work
Ocarinas work by creating oscillations within a hollow chamber using a 'voicing' consisting of the following components:
- Wind way
- Sound hole
- Labium
- Chamber
- Finger holes
When you blow an ocarina, the windway focuses the air into a flat sheet that travels across the sound hole. As it does so, it pulls additional air with it, due to the Bernoulli principle. Depending on the pressure within the chamber, the airstream from the windway will either go towards the outside, or inside of the instrument:
- If the pressure within the chamber is high, the airflow bends towards the outside, pulling air out of the chamber and leaving it at a lower pressure.
- If the pressure within the chamber is low, the airflow bends to direct air into the chamber, leaving it at a higher pressure.
The instrument alternates between these two states, creating oscillations that we hear as sound. This mechanism is called an 'air reed' because the vibration of the airflow serves the same function as a vibrating reed in an instrument like a clarinet or harmonica.
The pitch produced—the highness or lowness of the sound—varies depending on many factors:
- How hard the instrument is blown, the pitch raises as it is blown harder.
- The volume of the chamber, larger chamber volume results in a lower pitch.
- Ambient air temperature, the higher the temperature, the higher the pitch.
Note that only the air is vibrating. The material of the instrument is just acting as a container and has very little impact on the sound.
Finger holes: changing the pitch
In addition to blowing pressure, the pitch (note) sounded by an ocarina can be changed by opening holes in its surface. Adding a hole raises the pitch by allowing the air to flow in and out of the chamber more easily.
The pitch is controlled by the size of the open holes, for example in a microtonal ocarina where the pitch will lower as the player moves their hand to cover more of a single large hole.
But to make it easier to attain a given pitch, ocarinas are designed with a fingering system using multiple holes. The pitch produced is determined by the area of all of the open holes combined.
Unlike tubular instruments, the exact locations of the finger holes on an ocarina does not matter that much. The entire chamber is always oscillating, and the holes are placed to be ergonomic for the player.
Why ocarinas have limited range
While the pitch of an ocarina is determined by the total area of the open finger holes, we cannot keep adding more holes to infinitely increase the range of notes we can play.
Opening holes allows the air entering and leaving the chamber to move faster, but it also means that the air can escape more easily; you have to blow harder and harder to maintain pressure in the chamber.
Past a certain point, it is no longer possible to compensate for the air being lost. The sound becomes more airy, and eventually the instrument stops sounding entirely.
The exact range which can be attained from a single chamber is slightly more than an octave. It does vary with the quality of the ocarina, but there is always a trade-off between range and the clarity of the high notes.
Sounding range and chamber volume
The range that an ocarina is capable of producing has some connection to total chamber volume. Ocarinas with a smaller chamber volume tend to be able to sound a larger range:
- High pitched (soprano) ocarinas can easily produce a range of 21 chromatic notes (12 finger holes), without the high notes being notably airy.
- Low pitched (bass / contrabass) ocarinas produce a range of about 18 chromatic notes (10 finger holes), and can still sound more airy on the high notes.
Exactly why this happens I am not completely sure, it seems to be a combination of factors:
- Smaller chambers contain a much lower mass of air, and require less energy to drive.
- In larger ocarinas, the sound hole is smaller in relation to the volume of the chamber.
- Smaller chambers use smaller sound holes, the air has less distance to travel before it reaches the labium, and this leads to it being less turbulent, due to the physics of airflows.
But because of these limitations, it does not make sense to expect a low-pitched ocarina to behave and finger identically to a high-pitched ocarina.
The voicing neck
One way that makers work around the reduction of range in low-pitched ocarinas is to set back the sound hole into the mouthpiece, in a constrained volume I call the 'voicing neck'.
Effectively, the range that an ocarina can attain is limited by the volume of the chamber, as this limits how many holes can be opened before sound production breaks down.
The voicing neck traps a plug of air which slows down the oscillations, allowing the same low note to be attained with a smaller chamber. In turn, that increases the headroom in the high notes.
In practice, voicing necks are mostly found on lower pitched ocarinas, as the narrow diameter of the chamber in a soprano ocarina serves the same function. As an ocarina gets larger and lower pitched, more neck is required to prevent the required chamber volume expanding uncontrollably.
Being aware of the voicing neck as an ocarina player is useful for:
- Estimating how an ocarina will play without being able to play it.
- Identifying poor quality instruments.
For example, ocarinas with a more pronounced neck tend to be quieter and more balanced in volume and timbre over their range. If you see a large bass ocarina with no neck, there's a good chance that the high notes will be airy.
Closing notes
Having a basic awareness of how ocarinas work helps to estimate how a given ocarina will play without needing to play it. It also answers other common questions like 'why does my ocarina have airy high notes'.
Ocarinas are limited instruments. They function best when in harmony with their physical limitations, not in conflict with them. In single chambers, that means finding a good compromise between range and balanced timbre.
As you get more experience and play a wider variety of ocarinas, you'll start to recognise certain patterns in their design, and how those contribute to certain playing characteristics.
Through the following articles, we'll be exploring various aspects of an ocarina's playing characteristics, such as how the shape of the sound hole can result in timbres ranging from pure to buzzy, and factors that influence the instrument's volume dynamics.
