The ocarina's breath curve and tuning
Put simply, an ocarina's breath curve is how your blowing pressure must change over an ocarinas range in order to play in tune, and produce a clean sound.
For an ocarina to produce a strong tone, the voicing has to push air into the chamber faster than it can escape through the finger holes.
So, on the low notes when most of the holes are closed, little air is required, and as you play higher notes more is needed. We call these pressures the breath curve.
If you were to measure them and make a graph, they would form a curve something like this. The ocarina's natural pressure curve is approximately exponential:
Now, every single ocarina has a different breath curve. Some require only a small pressure change, whereas others ramp up hugely towards the high notes. The exact shape of this breath curve depends on quite a lot of factors including:
- Chamber volume.
- The size of the sound hole.
- The distance to the labium.
- How restricted the windway is.
- How the maker tuned the ocarina.
A breath curve can be steep or shallow, as shown in the following graph.
With a little experience you can pretty accurately guess how an ocarina's breath curve is going to be by looking at its visuals. The sizes of the finger holes are very telling as tuning with a steeper breath curve results in larger holes.
Ocarinas can produce the same pitch with quite different chamber volumes. An ocarina that is large for it's pitch, with a large sound hole is also going to play at a higher pressure.
It is really valuable to try playing a range of ocarinas made by different makers and observe how the breath curves are different. How to quantify it is discussed in Measuring an ocarina's breath curve.
Hole count and breath curve shape
It is worth noting that the number of finger holes impacts the shape of an ocarina's breath curve . As the breath curve is exponential, every additional hole significantly increases the pressure required to sound the high note.
Consequently, a 10 hole ocarina may be tuned with a flatter breath curve than a 12 hole, if both follow the same design. Multichambers may also have a flatter breath curve, as each chamber produces a smaller part of the total range.
Breath curves and sounding volume
The shape of an ocarina's breath curve has a big impact on how it plays and sounds:
- Steeper breath curves result in a louder instrument, and also increase the difference in volume between the high and low notes. Steeper breath curves also demand more from the player, as there is a larger pressure change between notes.
- Flatter breath curves have the opposite characteristic: their volume is more balanced over the range, and such instruments are typically easier to play at higher tempos.
Which of these factors is desirable varies depending on what you are trying to do with the ocarina. A steep breath curve can be useful if you are playing outside or in a large room without amplification.
But do note that ocarinas are naturally loud on their high end, and a steep pressure curve often pushes that to an extreme. Amplification, on the other hand, can provide extra volume with a shallow breath curve.
Breath curves in multichamber ocarinas
The breath curves of multichamber ocarinas share the same characteristics and variation as single chambered ocarinas. They can be tuned with a shallower pressure curve, or alternately a steeper one.
Just note that the breath curve of each chamber is independent. Because an ocarina's breath curve is approximately exponential, maintaining a completely regular pressure change over the entirety of a multichamber is impossible, as the high notes would be tuned to an insanely high pressure and would squeak.
The point that the breath curve of the first chamber ends and the second starts is called the chamber break. Usually multichambered ocarinas are tuned so that the higher chamber starts at a similar preassure, and increases more gradually.
Sometimes there will be a pressure drop between chambers, which usually exists to allow the playing of harmonies between chambers.