Piano
The piano is a fixed-pitch, equal-tempered instrument: the player cannot bend or adjust pitch in real time. Its "intonation" is set entirely by the technician at tuning time. The defining characteristics are equal temperament, the Railsback stretched-octave curve (bass tuned flat, treble tuned sharp), string inharmonicity, and seasonal drift driven by humidity. Understanding them helps you hear when a piano needs service and how to play in tune *with* it.
Common Pitch Tendencies
- Equal temperament: every interval except the octave is a compromise — ET major thirds beat ~+14¢ sharp of just (5/4), fifths sit ~2¢ narrow of pure
- Stretched octaves (Railsback curve): the treble is tuned progressively sharp and the bass progressively flat of pure ET, caused by string inharmonicity
- The player cannot bend pitch — "tuning" the piano means awareness and reference, not embouchure or finger pressure
- Unisons (2–3 strings per note) and "false beats" are the most audible faults; a single mistuned string in a unison beats audibly even when the temperament is perfect
- Overall pitch tends to drift flat over time as strings relax, and globally with humidity as the soundboard swells or shrinks
- The temperament octave near the middle is tuned to pure ET first, then octaves are stretched outward from it toward the extremes
- Bass strings are the most inharmonic (short, thick, wound) — their sharp upper partials force the stretch widest at the keyboard ends
Temperature & Warm-up
Humidity is the dominant driver, more than temperature. In humid summers the soundboard crowns and pitch rises sharp; in dry winters it flattens and pitch drops flat — and unevenly across the scale. Tune at least twice a year (typically spring and fall), keep room humidity near 42% with a humidifier or a Dampp-Chaser system, and after a move let the piano acclimate to the new room for a few weeks before tuning.
Register Guide
bass
Bass (A0 up to roughly C3): tuned progressively FLAT of equal temperament — about -30¢ at A0 easing toward the middle. The thick, short, wound bass strings are highly inharmonic, so their octaves are stretched downward to beat pure against the sharp upper partials.
temperament
Temperament octave (around F3–F4, centered on middle C): tuned to pure equal temperament FIRST as the reference, with essentially no stretch. A=440 lives here. The technician sets all twelve ET intervals in this octave, then stretches outward from it in both directions.
treble
Treble (roughly C5 up to C8): tuned progressively SHARP of equal temperament — about +3¢ at C5 growing to +32¢ at C8. Thin, short treble strings are inharmonic, so octaves are stretched upward to keep them beat-free against the lower registers.
Note-by-Note Tendencies
| Note | Fingering / Position | Tendency | Adjustment |
|---|---|---|---|
| A0 (lowest key) | N/A | -30 | Stretched bass: tuned ~30¢ flat of ET so octaves beat pure against the inharmonic upper partials of the thick wound strings |
| C2 | N/A | -12 | Low bass still tuned flat of ET; inharmonicity is large here so the stretch is pronounced |
| C3 | N/A | -5 | Approaching the temperament region; the flat stretch tapers off toward middle C |
| C4 (middle C) | N/A | 0 | Center of the temperament octave — tuned to pure ET as the reference, essentially no stretch |
| A4 (A440) | N/A | 0 | The A=440 reference pitch the whole instrument is set from; the technician's fork/meter anchor |
| C5 | N/A | +3 | Stretch begins on the treble side: tuned slightly sharp of ET so octaves beat pure upward |
| C6 | N/A | +9 | Upper-treble stretch growing; sharpness of ET against the lower octave is deliberate, not an error |
| C7 | N/A | +18 | High treble tuned well sharp of ET; thin short strings are inharmonic so the partials demand the stretch |
| C8 (highest key) | N/A | +32 | Top of the Railsback curve: tuned ~32¢ sharp of ET so the top octaves still beat pure against the rest of the piano |
Equipment & Setup
tuning
- Tuning frequency: a piano in regular use needs tuning at least twice a year; concert and studio instruments far more often. New pianos need 3–4 tunings in the first year as strings stretch in
- A=440 reference: standard concert pitch in the US; some European halls and pianos sit at A=442 — confirm before tuning to another instrument
- Pitch raise: a piano left untuned for years drops well flat and needs a "pitch raise" pass before a fine tuning will hold
- Stretch is normal: a properly tuned piano measures sharp in the treble and flat in the bass on a non-stretching tuner — that is the Railsback curve, not a mistuning
environment
- Hygrometer: keep one in the room and aim for ~42% relative humidity year-round; swings, not absolute level, cause the most pitch movement
- Dampp-Chaser / climate-control system: an in-piano humidity system dramatically stabilizes tuning between visits in variable climates
- Placement: keep the piano on an interior wall, away from heating/AC vents, fireplaces, radiators, and direct sunlight — local heat sources detune sections unevenly
- Whole-room humidifier/dehumidifier: a steady room is the single biggest factor in how long a tuning holds
maintenance
- Regulation: periodic adjustment of the action (key dip, let-off, hammer travel) keeps touch even — it does not change pitch but is part of full service
- Voicing: hammer needling/shaping sets tone (mellow vs bright); separate from tuning but often done alongside it
- Unison and false-beat correction: the technician sets each note's 2–3 strings to a clean unison and addresses "false beats" from worn or fouled strings
- Move acclimation: after relocating the piano, wait a few weeks for it to settle into the new room's climate before booking a tuning
Practice Tips
- You can't bend a piano's pitch — so tune YOUR instrument to the piano, never the piano to you; sound a unison against a sustained piano note and match it
- In any ensemble with a piano, the piano is the fixed pitch reference: everyone else adjusts to equal temperament, accepting that ET thirds and sixths beat against just intervals
- Check a piano by ear before service: play octaves up the keyboard (clean, beat-free even when stretched) and unisons (no beating within a single note) — beating unisons are the clearest "needs tuning" sign
- Book tunings seasonally — right after the heating season starts and after it ends — so you tune through the humidity swing rather than chasing it
- Singers and string players: expect to sing/play ET major thirds slightly low and leading tones slightly high relative to your own just-intonation instinct when the piano holds the chord
- Digital pianos don't drift and never need tuning, but good ones emulate stretch tuning — if a digital sounds "dead" in octaves, check for a stretch-tuning or temperament setting
- Don't try to "fix" a stretched piano with a chromatic tuner — the treble reading sharp and bass reading flat is correct; a flat-tuned (un-stretched) piano sounds dull in octaves
- If only a few notes sound off, it's usually a single drifted string in a unison — a tuning will clear it; a note that's off across its whole register points to a section that moved with humidity
Common Brands & Models
Brands cataloged in Virtuosic for piano (used by the app to filter shared tendency data by manufacturer).
Ensemble Intonation
Ji Deltas Instrument
- major-third
- perfect-fifth
- major-sixth
Section Role
- The piano is a FIXED equal-tempered reference — it cannot bend pitch, so every other instrument and voice tunes TO it, never the reverse
- When the piano holds a chord, just intonation is off the table: its major thirds beat ~+14¢ sharp of just and its fifths sit ~2¢ narrow — singers and strings must accept ET
- Tune your A to the piano's A (usually A4=440): sound a unison and match the beat to zero before the rest of the ensemble tunes off you
- With a piano present the ensemble pitch center is locked to ET; without a piano, winds/strings/voices are free to lean into just intervals
- In a concerto, the soloist adjusts to the piano in rehearsal pitch checks even though both are nominally at A=440
Genre Pitch Center
- Classical / accompaniment: A=440 in the US; some European venues and instruments at A=442
- Jazz combo: A=440; the piano is the harmonic anchor the horns and bass tune to
- Pop / studio: A=440 standard; digital pianos and DAWs are dead-on ET with optional stretch
- Historical-performance keyboards (fortepiano, harpsichord): often A=415 (baroque) and frequently a non-ET historical temperament
References
Tendencies and adjustments are drawn from established acoustic-research and pedagogy literature for this instrument family. Specific cent values vary by individual instrument, player, and conditions.
- Railsback, O. L. (1938). Scale Temperament as Applied to Piano Tuning. JASA, 9(3), 274.
- Young, R. W. (1952). Inharmonicity of Plain Wire Piano Strings. JASA, 24(3), 267–273.
- Fletcher, N. H. & Rossing, T. D. (1998). The Physics of Musical Instruments (2nd ed.). Springer.
- Reblitz, A. A. (1993). Piano Servicing, Tuning, and Rebuilding (2nd ed.). Vestal Press.
- Jorgensen, O. H. (1991). Tuning. Michigan State University Press.
See your own intonation profile
Virtuosic Premium overlays your per-note pitch deltas on these instrument averages, so you can see exactly where you differ from the typical piano player — and how warmup shifts each note.