Pitch and Temperament Explained

To understand why tuning a piano is a craft rather than a mechanical chore, it helps to go one level deeper into the ideas of pitch and temperament. These concepts explain why a piano can be "in tune" and "slightly out of tune" at the same time, and why setting them by ear is a genuine skill.

What Pitch Really Is

Pitch is simply how high or low a note sounds, and it corresponds to the frequency at which a string vibrates, measured in hertz. The universal reference is A440: the A above middle C set to 440 vibrations per second. Fix that one note and, in principle, every other note follows from mathematical ratios. In practice, the tuner sets a foundation of notes in the middle of the keyboard first — the temperament octave — and tunes outward from there.

A440 became an international reference in the twentieth century so musicians everywhere could play together in agreement. Some ensembles deliberately tune slightly higher or lower for particular repertoire, but for pianos, A440 is the standard nearly all technicians work to.

Listening to Beats

When two strings vibrate at almost — but not exactly — the same frequency, the sound pulses, growing louder and softer in a regular throb. These pulses are called beats, and they are the tuner's most important tool. By counting the speed of the beats between two notes, a technician can measure how far apart they are with remarkable precision, far finer than simply judging "higher" or "lower."

Tuning unisons — the two or three strings that share a single note — means adjusting them until the beats disappear entirely and the strings sing as one. Setting the temperament means deliberately tuning certain intervals to beat at specific, controlled rates. It is, quite literally, tuning by counting.

Why Equal Temperament Is a Compromise

Here lies one of the elegant problems of music. The pure, beat-free intervals that the ear finds most consonant — perfect fifths and thirds derived from simple frequency ratios — cannot all coexist on a fixed-pitch instrument like a piano. If you tune a series of pure fifths up the keyboard, you arrive at a note that does not match the octave you should have landed on. Something has to give.

Equal temperament is the solution modern pianos use: the octave is divided into twelve exactly equal semitones, and the small unavoidable discrepancy is spread evenly across all keys. No interval except the octave is perfectly pure, but none is badly out either, and crucially, every key sounds equally usable. This is what lets composers write freely in any key and modulate between them — a freedom earlier tuning systems didn't fully allow.

A Brief History of Temperament

Before equal temperament became standard, keyboards used a variety of historical temperaments — systems like meantone and well-temperament that made some keys sound sweeter at the expense of others. Music of earlier eras was written with those colorful key characters in mind. As Western music grew more chromatic and adventurous in its use of distant keys, equal temperament's even-handed compromise won out. You can explore this rich history through resources such as Encyclopaedia Britannica.

Why This Matters to You

You don't need to count beats to enjoy your piano, but understanding temperament explains a few real-world things: why a good tuning sounds "alive" rather than mechanically perfect, why a skilled human ear still matters even with electronic tuning aids, and why two competent tunings can have subtly different character. It also underscores why the craft has endured for centuries. To see how these ideas play out in an actual tuning appointment, revisit how piano tuning works.