Things you need to know when composing for the ocarina
This page is a general overview of the ocarina's capability for people wishing to compose for the instrument. Please bare in mind that I am not a composer and these suggestions arose from discussions with several composers regarding the ocarina's capability. Also note that what is possible varies a great deal between players. Ocarinas have players from many different backgrounds, thus they approach playing in very different ways.
The ocarina is a fully chromatic instrument with a limited range: single chambered ocarinas can produce about an octave and a fourth (e.g. C5 to F7), with a triple chamber extending the high end beyond two octaves (see 'Ocarina keys and pitch ranges'). For any single fingering within this range, an ocarina will only play in tune at a single pressure. Additionally, ocarinas have an innate volume dynamic where the high notes are considerably louder than the low ones. Volume dynamics are technically attainable, but are difficult to achieve and are not common practice.
Some ocarinas can play 'subhole notes' below the note for their key, played by covering two holes with one finger. These notes however fall on the lowest end of the volume curve—they are quiet, have very unstable pitch (covered later), and normally have a pretty muddy timbre. Playing them fast is also an ergonomic challenge as sliding fingers is more difficult than lifting them. These can work effectively as weak beat notes or passing tones, but you generally don't want to start or finish a piece of music on one of these notes, unless you are deliberately going for a weak effect.
Writing for the ocarina requires a different approach to many instruments, as creating emphasis depends on both utilising the innate volume dynamic and making effective use of varied articulations and ornamentation. The musical function of the ocarina is pretty close to the tin whistle and certain kinds of bagpipe. They are loud and piercing, and almost always take the lead in a mix. As volume dynamics are technically difficult, varied articulations and ornaments are used instead.
Ocarinas typically play from standard music notation in the treble clef, and ones in different octaves are usually treated as a transposing instrument whereby middle C always refers to an ocarina's low C. Consequently, 'alto' ocarinas play an octave higher than written and 'soprano' two octaves higher. Ocarinas are commonly available in keys besides C, and these may be written at pitch or treated as transposing instruments.
Stating that an ocarina is 'in a key' can be misleading as ocarinas are fully chromatic. In this case, 'key' refers to an ocarina's base pitch. Retuning the whole instrument like this is not done to play in the named key per se but to gain access to a different range of notes, which is especially important with single chambers. Ocarinas are also available in different pitch ranges like bass (C4~), alto (C5~), and soprano (C6~), providing access to lower or higher notes.
Multichamber ocarinas extend the range of a single chamber upwards, a double alto C offering about two octaves from C5 to C7, with triples extending this further. This range is divided across at least two chambers. Each chamber is somewhat analogous to a single string on a chordophone, in that they must be fingered and played separately. Chambers are numbered starting from one and ascend upwards. The first chamber is responsible for the lowest notes, and subsequent chambers for higher ones.
There are two different tuning systems found on multichambers, Asian and Pacchioni. The Asian system provides the most range, whereas the Pacchioni system focuses on player convenience as chambers are tuned with an overlap. It should be noted that both of these designs exist primarily to extend the sounding range. In some situations it is possible to play chambers in harmony, but whether this will actually sound in tune varies between ocarinas.
It is easiest to move between notes on the same chamber. Moving between adjacent chambers is slightly slower, though still pretty fast. Making a leap across several chambers takes more time, as the instrument must move farther to reach the windway and fingers must move farther to the chamber. On Asian system multichambers, there is no note overlap between chambers, so you cannot 'cheat' as can be done on violin by changing positions. The Pacchioni system does provide an overlap and offers some of those benefits.
If you write for a multichamber, it is important to consider where these chamber switches are going to occur. Performing a switch usually requires tonguing the note (stopping the sound) to prevent off-sounds from being created. It is important to place these such that they are not awkwardly breaking up a phrase. On a double C, the break between the first and second chamber is between D and E in both the Asian and Pacchioni systems.
I noted before that an ocarina's pitch varies with blowing pressure. While this is true of all wind instruments, how the ocarina behaves is pretty unusual. The low notes are exceptionally sensitive to pressure changes and can easily be bent by multiple semitones. The high notes, on the other hand, are very insensitive to pressure changes, and only bend about a quarter tone before they start to sound bad.
The pressure difference between the low and high notes is also a lot more pronounced than many other instruments. This is because the ocarina is a lossy instrument: as holes are opened, more air can escape, and the player must blow harder to maintain a strong sound. This difference is called the breath curve and varies quite a bit between different ocarinas. Louder instruments using more pressure have a steeper curve.
These two factors combined mean that ocarinas are easiest to play in a relatively stepwise fashion. Making large leaps on the ocarina is possible but poses a few challenges. When leaping from a high note to a low note, it is easy to land out of tune as the low notes are so much less stable. This is easier, however, between the higher chambers of a multi. As they produce a smaller range, they are usually tuned with a flatter breath curve. Due to the forced volume dynamic, patterns that repeatedly leap between a low note and high note frequently sound unbalanced.