The ocarina's breath curve

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. Because of this the low notes require little air to sound. As higher notes are played there are more holes for air to escape, you have to blow harder or the tone becomes more and more airy. The total difference between the low and high end is called the breath curve.

You may have seen references to 'type one' and 'type two' ocarinas. Type one referring to a breath curve with little pressure change between the high and low notes. Type 2 referring to a breath curve which requires the pressure to be raised. See the diagram below.

In reality this strict distinction does not exist as there is a spectrum between the two extremes. The ocarina's natural pressure curve is approximately exponential, meaning that the pressure change from note to note increases as you go up the range. The exact shape of this breath curve depends on quite a lot of variables including chamber volume, the size of the sound hole, the distance to the labium, how restricted the windway is, and how the ocarina was tuned.

For any fingering, if breath preassure is changed tone clarity also changes. When too little preassure is used the instrument produces a very airy sound. As preassure is raised further this starts to sound cleaner, and continuing further makes the instrument sound more airy harsh, and will eventually squeak. Ocarinas are tuned such that the desired notes play in tune within a preassure range that sounds good.

Ocarinas made to play at a low pressure (green curve) will naturally have a flatter breath curve as less energy is needed to drive the chamber. Designing an ocarina to be louder, with a larger chamber volume and higher tuning pressure demands a considerably larger pressure change between the low and high notes, or high note tone will suffer. Hole size somewhat indicates where an ocarina falls in this range, as increasing tuning pressure results in larger holes.

Another big factor affecting the shape of an ocarina's breath curve is how many holes the instrument has. As the breath curve is exponential every additional hole significantly increases the pressure required to sound the high note. This in turn increases the pressure difference between the low and high end. A 10 hole ocarina may be tuned with a flatter breath curve over its sounding range than a 12 hole. Multichambers may also have a flatter breath curve, as each chamber produces a smaller part of the range.

Breath curves have a number of effects. An ocarina with a steeper breath curve will generally be louder. However such instruments require more effort to play and can be difficult to play quickly. When a breath curve is steeper, there is a larger pressure change between notes, and this requires more effort from the player. A flatter breath curve will have a more balanced volume over their range, and are easier to play quickly.

Steeper breath curves will also be louder on the high end, but I don't see a lot of value to this. Ocarinas are naturally loud on their high end and a steep pressure curve may push that to an extreme, such instruments will only be viable if the volume dynamic of the music you are playing happens to benefit from an exceptionally loud high end.

Measuring the breath curve

Directly measuring an ocarina's breath curve is prittu difficult as the pressures are so low, but it can be judged indirectly. It can be checked by measuring the tuning of two adjacent notes, where they are both blown at the same pressure. Using a chromatic tuner, blow a lower note and, without changing your pressure, raise the finger for the next note in sequence. The higher note will fall flat. Begin at your ocarina's lowest note and check them all sequentially; their flatness should be fairly consistent but may increase or decrease gradually between sequential notes. Note that if you are blowing your ocarina to concert pitch, these results will change with temperature.

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