Tuning forks for music.

Why musicians still use a tuning fork

From its invention in 1711 by the British musician John Shore until electronic tuners arrived, the tuning fork was how music carried its pitch from place to place. Electronic tuners have largely replaced it, and most orchestras today tune to an A given by the oboe, which the oboist usually checks against an electronic device.

The fork has kept its place for a few simple reasons. It needs no battery and has no settings to get wrong. Its tone is almost a pure sine wave, so the pitch is easy to hear. And it trains the ear: instead of watching a needle, you learn to hear when two notes agree. Many piano tuners still set their first note from a fork, and it remains a simple way to practise tuning by ear.

Which tuning fork do you need?

A musical fork is marked with a note and a frequency. Buy the one that matches the pitch your instrument or ensemble uses.

If you are unsure, choose A = 440 Hz. It is the note almost every tuner, app, keyboard and recording assumes.

How to tune a guitar with a tuning fork

With an A 440 fork, you tune the fifth string first. The open A string sounds 110 Hz, two octaves below the fork. The natural harmonic at the 5th fret of that string sounds two octaves higher, exactly the fork's A4, so you can compare them directly.

• Strike the fork on your knee or a rubber pad, never on the guitar or a hard edge.
• Press the end of the stem onto the bridge or the top of the guitar near the bridge. The body acts as a soundboard and the tone becomes clearly audible, and your hands stay free.
• Lightly touch the A string directly above the 5th fret wire, without pressing it down, and pluck it. You hear a bell-like harmonic.
• Listen for beats, a slow pulsing in volume. Turn the tuning peg: if the beats speed up you are moving away, if they slow down you are getting closer.
• When the pulsing stops, the string is in tune. Tune the other strings to the A string in your usual way, by fretted notes or harmonics.

With an E fork (329.63 Hz), it is even simpler. The open high E string sounds the same E4 as the fork, so you strike the fork, pluck the open first string and match them without harmonics.

What are beats, and why do they help?

When two tones are close but not identical, they drift in and out of step. You hear this as a regular swelling and fading of volume. The rate of these beats equals the difference between the two frequencies. A fork at 440 Hz and a string at 442 Hz beat twice per second. At 441 Hz, once per second. At 440 Hz, the beating stops.

That is why a fork can be very precise even for an untrained ear. You do not need to judge whether a note is high or low in the abstract. You only need to hear a pulse slow down and vanish. Piano and organ tuners use the same principle, counting beat rates on purpose when they set the intervals of a temperament.

Other instruments: violin, piano, voice

• Violin and viola: the A string is A4, the same note as a 440 fork. Tune it to the fork, then tune the other strings in fifths from it. The cello's A string sounds one octave lower, at 220 Hz.
• Piano: tuners usually set one note from an A440 or C523.25 fork, then tune a middle octave, often F3 to F4, by ear and extend it across the keyboard. This is skilled work; a fork alone will not tune a piano.
• Voices and choirs: a conductor or singer strikes the fork, holds it near the ear or presses it on a table, and hums the note to find the starting pitch of an unaccompanied piece.

Musical forks and other forks

A musical tuning fork is usually unweighted, with plain prongs, and designed to ring clearly in the air. Medical forks, such as the 128 Hz fork with weights used to test vibration sense, are made for examination, not for tuning. Some forks sold in sets for sound practices are tuned to pitches that do not match any musical scale, so check the note before you rely on one for an instrument.

A steel fork is very stable. Its pitch changes by about 86 parts per million per degree Celsius, so a 10 °C swing moves a 440 Hz fork by less than half a hertz. The string you are tuning will drift far more than that.

Where our 432 Hz fork fits

The Cosmic Wishing Fork is tuned to 432 Hz, an A about a third of a semitone below concert pitch. It is made to be worn, in 316L stainless steel, and it rings a real, clean tone. But it is a ritual object for a moment of pause, not a tool for tuning a band to A440. If you play with others, tune to 440 Hz. If you want a tone to carry with you, join the waiting list.