Improving the design of tunable ocarinas

The pitch of all wind instruments depends on temperature. While the ocarinas pitch is sensitive to changes in breath preasure, as I have previously demonstrated, they do not respond linearly to these changes across there sounding range. If the pitch is raised on the low end by blowing harder, a notably larger increase in pressure is required to attain the same gain in pitch on an ocarinas high notes, shown by the diverging curves:

Within small temperature variations this is not a great issue, however it becomes more so when one must play in temperatures much colder or warmer than the ocarina was tuned for. In colder environments as the pressure is raised on the high notes there tone becomes increasingly airy, and at some point they will start to squeak. It is also troublesome for a player as it alters how much the breath must change to land an interval in tune. The player must acclimatise themselves to these differences every time they play.

When playing in a relatively temperature stable environment this is not too much of a problem, however when doing live performances the musician has little control over the ambient temperature.

Re-tuning accompaniment provides a solution, but may not be possible if one is playing with fixed-pitch instruments. One could also compensate by having a number off ocarinas tuned to different temperatures, however as multiple ocarinas in different keys are often required due to the instruments limited range, a lot of ocarinas would be needed. This would quickly become impractical. Because of these factors I see value in the concept of a tunable ocarina.

As the high notes are less sensitive to changes in breath pressure, any pitch change resulting from a tuning device will be most obvious on these notes. Consequently when evaluating the effectiveness of a tunable ocarina, any measurements should be made on the high notes. The low end is much more sensitive to changes in breath pressure and consequently the effect of a tuning slide is much more difficult to distinguish from subtle changes in blowing pressure.

As the main issue created by temperature shift is with the high notes needing a greater change than the low to maintain a given pitch shift. I feel that reducing this should be the main focus when designing a tunable ocarina, reducing the divergence of the pressure curves.

Allowing the high notes to be played with less pressure in a cold environment, and increasing the pressure in a hot one will allow these notes to play in tune with optimal tone. Maintaining a consistent breath curve is also desirable for players as it may be more easily learned to muscle memory. This should ease the issue of landing wide leaps in tune.

The concept of a tunable ocarina is not new, there are historic examples of them in the ocarina museum in Budrio. All such designs revolve around the idea of inserting a moveable plunger or rod into the chamber volume, which displaces a portion of the volume, depending on how much it is slid in or out.

This idea is problematic for a number of reasons. Firstly the volume displaced by such a plunger is generally small, making it have little effect on the pitch. For a plunger to have a worthwhile change to the tuning it would need to have a large diameter.

The pitch of a hole may be lowered by 'shading' it, placing an obstruction close to a hole, yet not totally sealing it. Consequently in higher keyed ocarinas, which by necessity use a long and narrow chamber, a plunger of notable diameter inserted into the chamber will shade the insides of the left hand holes.

Because this shading will lower the pitch of certain holes, the breath curve would need to change in order to maintain the desired pitch. As the goal of a tunable ocarina is to reduce change in the breath curve, I consider this situation undesirable.

I believe it would be superior to move the tuning plunger into a separate sub-volume attached to the main chamber. As it is separate volume and not close to any finger holes the tuning plunger can never shade them. In order to maximise it's effectiveness the 'tuning volume' should be of large diameter. The volume should be a parallel tube, sealed at one end by the tuning plunger, like the piston in an engine. Consequently I feel it would be more appropriately called a 'tuning plug'. This plug may be moved in/out to change the volume of the sub-volume, adding/removing volume from the master chamber.

I have tried this idea on my alto D, in this case it allows the pitch of the highest note to be shifted by approximately 30 cents. There is plenty of headroom to improve on this result, firstly the diameter of the tuning volume could be at least doubled, bringing it close to the diameter of the chamber.

Secondly the tuning plug was cast from silicone sealant and it's surface is pitted due to trapped air bubbles. Because of which it does not seal optimally, especially when slid out. A leak will have the effect of adding an additional small hole to the chamber, raising the pitch and counteracting the pitch reduction from increased chamber volume.

Tuning plug pushed in

Tuning plug pulled out.

Side view.

Applying this to multi chamber ocarinas