How to improve the effectiveness of tunable ocarinas

Current tunable ocarinas are based on the idea of inserting a tuning rod into the chamber. By sliding in or out, it occupies part of the chamber volume, changing the pitch.

This design has existed for a long time, with historic examples in the ocarina museum in Budrio. However, it also isn't very effective. In this article I'm going to explain the value of tunable ocarinas for players, and explore some ways of improving them.

Rationale

To begin, I feel it is worth explaining why a tunable ocarina is even needed, given that an ocarina's pitch can already change a great deal with blowing pressure. Understanding this also demonstrates how to measure the effectiveness of an ocarina tuning mechanism, which isn't so intuitive.

As I have previously demonstrated, an ocarina's pitch responds nonlinearly to changes in blowing pressure over its sounding range. Consequently, when playing in a colder environment, the player needs to increase their blowing pressure more on the high notes than the low. In a warmer environment, the effect is reversed.

When the needed compensation is small, this isn't a huge issue, but at larger ones it has a number of negative effects:

• An ocarina's high notes sound best within a relatively narrow pressure bend, and greatly under or over blowing them for tuning compensation will not produce optimal tone.
• Playing in a colder environment and blowing up to pitch increases the pressure difference between the high and low notes, making it harder to play fast music.
• Needing to learn multiple pressure curves for different environments creates unneeded practice work for a player.

An effective tunable ocarina would solve all of these problems, allowing the pressure required to sound the high notes to be brought back into an optimal range.

It should also be apparent that it is important to measure the effectiveness of a tuning slide using an ocarina's high notes. The influence of a tuning slide on the low notes can be almost imperceptible as they are already very sensitive to pressure changes.

Why existing tunable ocarinas are not effective

The reason why the existing design used by tunable ocarinas isn't very effective is the diameter of the plunger. Tuning plungers usually occupy a negligible volume in proportion to the total volume of the chamber.

Thus, an obvious way of improving the effectiveness of tunable ocarinas is to just increase the diameter and length of the tuning plunger. To some extent this will work, but:

• The pitch produced by a tone hole will be lowered by an object in proximity to it, even if it is not closing the hole. An effect called shading.
• Due to shading, you cannot stick an arbitrarily large diameter plunger into a chamber, as it will alter the tuning of the shaded finger holes, spoiling the tuning.
• A large tuning plunger may have notable mass, and moving it will undesirably affect the physical balance of the whole instrument.

A different approach

The problems noted in the previous section arise from the conflict between the normal function of the chamber and the tuning plunger. An obvious way of solving the problem is to separate these concerns by introducing a secondary tuning volume separate to the main chamber:

• Make the main chamber volume smaller
• Attach a secondary 'tuning volume' which can be varied

In order to maximise its effectiveness the 'tuning volume' should be of large diameter. The volume should be a parallel tube, sealed at one end by the tuning plug, like the piston in an engine.

This plug may be moved in/out to change the volume of the sub-volume, adding/removing volume from the master chamber. As it is separate volume and not close to any finger holes the tuning plunger can never shade them.

I have tried this idea on my alto D and in principle it works. This first attempt allows the pitch of the highest note to be shifted by approximately 30 cents, with obvious improvements available:

• I made the diameter of the tuning volume too small, and it could be increased to match the diameter of the chamber.
• The tuning plug seals poorly, reducing effectiveness. It was cast with silicone, and its surface is pitted due to trapped air bubbles. Improving the manufacturing process of this would improve its effectiveness

Side view.

Ergonomics and closing notes

Before finishing, I'd like to note some points about this design. Positioning the tuning volume where I did, besides the mouthpiece, may seem weird. Intuitively, one may think that the tuning plunger would hit the players face, but it does not as the human face is not a flat plain.

This location was chosen due to a number of considerations:

• Due to the nature of the ocarina's acoustics, the volume must be attached to a large diameter part of the chamber
• Adding the tube for the tuning plug adds additional weight to the instrument. Positioning it in this location does not negatively affect ergonomics as it shifts the centre of balance towards the mouthpiece. Having the ocarina balanced to roll towards the mouthpiece is not a problem.
• Other locations have undesirable ergonomic effects. Placing it on the end of the chamber would shift the balance point left, and notably increase the perceived weight of the instrument. It could also harm the ergonomic function of the capello.
• Positioning it opposite the mouthpiece would be terrible as it would interfere with the player's hands, and cause the ocarina to roll forwards which is very poor ergonomic behaviour.
• Positioning it on the bottom of the chamber would interfere with the air leaving the voicing and result in worse tone. Opposite the mouthpiece would cause the ocarina to balance such that it would roll away from the mouthpiece, which you don't want.

Finally, this idea can be extended to multichambered ocarinas, which I explore in the article A design for a tunable multichamber ocarina