Why does my ocarina sound out of tune?
The most common reasons that an ocarina will sound out of tune are using the wrong breath pressure, or playing a poor instrument.
You may be blowing too hard or too soft
An ocarina's pitch changes significantly with blowing pressure. Consequently, blowing too hard or too soft will push the pitch sharp or flat.
Each note will sound in tune at only one pressure; the lowest notes need the least, and the highest the most. How this pressure changes from note to note is called the breath curve.
Breath curves vary enormously from maker to maker, so there is no single definition of what an 'in tune' ocarina is. In some ocarinas, pressure increases regularly from note to note, while in others, it increases exponentially. Some require the slightest pressure, whereas others need a lot.
To play in tune, you have to change your breath pressure to match your instrument's unique curve. This skill can be learned using a chromatic tuner and by playing with accompaniment. This is covered in detail on the page 'Playing the ocarina in tune'.
Also note that the absolute pitch of an ocarina is temperature sensitive. If you are playing in an environment notably colder than the ocarina was tuned for, it may be impossible to play in concert pitch, as the instrument will squeak on the high notes. The ocarina will still play in tune with itself, but at a flatter pitch.
Your ocarina may not be tuned properly
A lot of what is sold under the name 'ocarina' in mainstream outlets are poorly made. If the ocarina was very cheap, there is a good chance it is untuned or badly tuned.
The clearest tell that an ocarina is not tuned correctly is if all of the finger holes are identically sized, however instruments may also have tuning errors which are not visually obvious. You can check the tuning of an ocarina by playing sequential notes at the same pressure and noticing the pitch change using a chromatic tuner, see the article Recognising badly tuned ocarinas.
In case you do find that your ocarina is not tuned properly I'd strongly recommend getting a better instrument. There is advice on finding quality ocarinas in the article 'Identifying playable ocarinas'.
