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What Is Piano Tuning?

Piano tuning is the process of adjusting the tension of a piano’s roughly 230 strings so that each note sounds at the correct pitch and the intervals between notes are musically pleasing. A professional piano tuner — more accurately called a piano technician — uses a specialized wrench (tuning lever or tuning hammer) to turn the tuning pins that hold each string, tightening or loosening them until the pitch is right. The whole process takes about 1-2 hours and needs to be repeated roughly every six months.

Why Pianos Go Out of Tune

A piano is a machine under enormous stress. Those 230 strings exert a combined tension of about 15-20 tons on the cast iron frame. The strings are anchored to tuning pins driven into a laminated wooden pin block. Everything is mounted on or connected to a wooden soundboard.

Wood is hygroscopic — it absorbs and releases moisture depending on humidity. When humidity rises, the soundboard swells and crowns upward, increasing string tension and raising pitch. When humidity drops, the soundboard flattens, decreasing tension and lowering pitch. This is the primary reason pianos go out of tune.

Temperature changes matter too, though less than humidity. String tension naturally decreases over time as steel strings stretch and settle. New pianos are especially unstable — the strings haven’t fully stretched, and the pin block hasn’t fully compressed around the tuning pins. That’s why new pianos need frequent tuning in their first year.

Heavy playing accelerates pitch drift. Concert pianos are tuned before every performance — sometimes during intermission — because the force of a professional pianist’s playing measurably affects string tension.

The Tuning Process

A tuner arrives with a tuning lever (a specialized T-shaped wrench), a set of rubber mutes, and usually an electronic tuning device (though some tuners work entirely by ear).

Setting the temperament. The tuner starts by tuning the temperament octave — usually the octave around middle C. This involves setting the intervals between notes according to equal temperament (more on that below). The tuner plays pairs of notes, listens to the beat rate (the wavering sound produced when two nearly-in-tune notes sound together), and adjusts until the beat rates are correct.

Tuning octaves. From the temperament octave, the tuner works outward — tuning each note to be a perfect octave above or below its already-tuned neighbor. Octaves should sound pure, without beating.

Muting. Since most notes have two or three strings, the tuner mutes the strings they’re not currently tuning with rubber wedges. They tune one string per note first, then tune the remaining strings to match — a process called “setting unisons.” Unisons that are even slightly off produce a noticeable wavering.

Checking. The tuner plays chords, scales, and passages throughout the keyboard to verify that the tuning is consistent and musical. Small adjustments follow.

The whole process requires exceptional listening skills. Tuners are detecting differences in frequency measured in fractions of a hertz — far smaller than what untrained ears can perceive.

Equal Temperament (The Compromise)

Here’s a fact that surprises most people: a well-tuned piano is, mathematically speaking, slightly out of tune. Deliberately.

The problem is fundamental. In nature, musical intervals are defined by simple frequency ratios. A perfect fifth (C to G) should be a 3:2 ratio. A perfect fourth should be 4:3. A major third should be 5:4. But when you stack these perfect intervals around the circle of twelve notes, they don’t add up — twelve perfect fifths overshoots seven octaves by about a quarter of a semitone (the Pythagorean comma).

You can tune some intervals perfectly, but then others will sound terrible. For centuries, various tuning systems (temperaments) tried different compromises — making some keys sound great at the expense of others.

Equal temperament, the system used on modern pianos, divides the octave into twelve exactly equal semitones. Every semitone is a frequency ratio of the twelfth root of 2 (approximately 1.05946). This means no interval except the octave is acoustically perfect. Every fifth is slightly narrow. Every third is slightly wide. But the compromise is distributed equally across all keys, so every key sounds equally “good” (or equally imperfect, depending on your perspective).

J.S. Bach’s Well-Tempered Clavier (1722, 1742) — featuring preludes and fugues in all 24 major and minor keys — demonstrated the musical possibilities of a temperament that worked in all keys. It wasn’t quite equal temperament, but it was heading in that direction.

Pitch Raises

A piano that hasn’t been tuned in years often drifts flat — sometimes by a semitone or more. You can’t simply tune it back to standard pitch (A4 = 440 Hz) in one pass, because adjusting any string changes the tension on the frame, which affects every other string.

The solution is a pitch raise: a rough first pass that brings all strings approximately up to pitch, followed by a fine tuning pass. Severely flat pianos may need two or three pitch raises before they’ll hold a stable fine tuning. This is more time-consuming and expensive than routine maintenance — which is why regular tuning saves money in the long run.

The Tuner’s Ear

Professional piano tuners train for years. The Piano Technicians Guild (PTG) offers the Registered Piano Technician (RPT) certification, which requires passing rigorous written and practical exams covering tuning, regulation, and repair.

Some tuners work entirely by ear, using beat rates to set the temperament and check octaves. Others use electronic tuning devices (ETDs) that measure frequency precisely. The debate between aural and electronic tuning is passionate and ongoing — purists argue that a skilled ear produces more musical results, while pragmatists note that ETDs are more consistent and faster.

In practice, the best tuners combine both approaches — using electronic assistance for precision while relying on trained ears for the subtle musical judgments that make a tuning sound alive rather than mechanical.

A well-tuned piano is one of life’s quiet pleasures. Every note rings clearly, chords shimmer, and the instrument responds to your touch with clarity and warmth. A piano out of tune sounds muddy, sour, and vaguely wrong — even to people who can’t identify the problem. Tuning is the invisible maintenance that keeps the instrument doing what it was designed to do: turn mechanical energy into music.

Frequently Asked Questions

How often should a piano be tuned?

Most manufacturers recommend tuning twice a year — typically when seasonal humidity changes are greatest (spring and fall). New pianos may need tuning 3-4 times in the first year as strings stretch and settle. Concert pianos are tuned before every performance. A piano that hasn't been tuned in years may need multiple tuning sessions (pitch raises) to bring it back to standard pitch, as large adjustments don't hold well in a single pass.

How much does piano tuning cost?

A standard tuning costs $100-$200 in most areas, depending on location and the tuner's experience. If the piano is significantly out of tune and needs a pitch raise (bringing the overall pitch up before fine-tuning), the cost increases to $150-$300. Repairs beyond tuning — replacing broken strings, reshaping hammers, regulating the action — are billed separately and can add hundreds of dollars.

Why do pianos go out of tune?

The primary cause is humidity changes. Wood expands when humidity rises and contracts when it falls. The soundboard's expansion and contraction changes the tension on the strings, altering their pitch. Temperature changes also affect tuning. String tension naturally decreases over time as strings stretch. Heavy playing can accelerate pitch changes. Even a piano in a climate-controlled room will drift out of tune over months.

Further Reading

• Piano Technicians Guild
• Britannica - Musical Tuning and Temperament
• Acoustical Society of America