Piano

The piano is a percussive keyboard instrument, in which an action of felt-covered hammers strike strings stretched on a metal frame attached to a resonant soundboard.

The history of the piano is closely intertwined with the standardization of 12edo in the West. The development of steel frames with precision machining gave them the necessary capacity to hold the high level of tension (180–300 kN) to remain in tune reliably over time.

The piano can be used to play microtonal music in a variety of ways. A single piano's strings can be retuned. Like other keyboard instruments, the strong advantage that this provides for microtonal music is that due to pitch exactness and precision machining, an acoustic piano can also be constructed or rebuilt for essentially arbitrary pitches and tuning systems, satisfying any exact pitch placement that desired.

However, large departures from intended tuning, for example, from 12edo ― require changes to string length, gauge, tension, scaling, or even the frame and soundboard, rather than simply retuning the existing strings. A typical piano will only handle about a semitone of retuning before breaking strings becomes an issue. Additionally, excessive string stretching produces a timbre that sounds increasingly inharmonic and more bell-like.

As such, purpose-built microtonal pianos are required to accommodate tunings that would be impractical or unsafe to realize by retuning a conventional piano. Likewise, multiple pianos can be used: a solo player can play two keyboards at a right angle, or many players can play many pianos.

Electronic plugins like Pianoteq can be used to retune a modeled piano to arbitrary pitches with high precision, without the mechanical limitations that are found in the process of building a physical instrument.

Retuned standard piano

Ben Johnston used pianos tuned in 12-tone just intonation scales for his Sonata for Microtonal Piano (1964) and Suite for Microtonal Piano (1978).

The table below shows the tunings used in Terry Riley's The Harp of New Albion (1986), La Monte Young's The Well-Tuned Piano (1964-present), and Michael Harrison's Revelation (2007).

Harp of New Albion		The Well-Tuned Piano		Revelation
Ratio	Cents	Ratio	Cents	Ratio	Cents
1/1	0	1/1	0	1/1	0
16/15	112	567/512	177	567/512	177
9/8	204	9/8	204	9/8	204
6/5	316	147/128	240	81/64	408
5/4	386	21/16	471	21/16	471
4/3	498	1323/1024	444	729/512	612
64/45	610	189/128	675	189/128	675
3/2	702	3/2	702	3/2	702
8/5	814	49/32	738	27/16	906
5/3	884	7/4	969	7/4	969
16/9	996	441/256	942	243/128	1110
15/8	1088	63/32	1173	63/32	1173

Kyle Gann's Hyperchromatica (2018) was written for three Disklavier pianos with the just tunings shown in the table below.

Piano 1		Piano 2		Piano 3
Ratio	Cents	Ratio	Cents	Ratio	Cents
1/1	0	121/64	1103	63/32	1173
135/128	92	33/32	53	65/64	27
35/32	155	143/128	192	143/128	192
9/8	204	75/64	275	75/64	275
5/4	386	77/64	320	39/32	342
21/16	471	165/128	440	81/64	408
11/8	551	11/8	551	169/128	481
3/2	702	45/32	590	91/64	609
49/32	738	99/64	755	195/128	729
105/64	857	25/16	773	13/8	841
7/4	969	55/32	938	27/16	906
15/8	1088	225/128	977	117/64	1044

Arnold Dreyblatt employed a 40-key miniature pianoforte in his Orchestra of Excited Strings, tuned to the 11-limit Dreyblatt tuning system.

Two standard pianos a quarter-tone apart

Two standard pianos tuned a quarter-tone apart can be used to play music in 24edo. Examples include Charles Ives' Three Quarter-Tone Pieces (1924), Ivan Wyschnegradsky's 24 Préludes (1934), and John Eaton's Microtonal Fantasy (1965).

Retuning two pianos

In 1992, Georg Hajdu published a report of the "17 Tones" project, in which five composers wrote music featuring two player pianos tuned to 17edo.

In 2006-2008, Jacob Barton had two surplus grand pianos tuned to 17edo and produced the Seventeen Tone Piano Project, a series of four calls for works and concerts at Rice University.

In 2008, Aaron Krister Johnson produced an event featuring two upright pianos tuned to 19edo as part of Midwest MicroFest (now UnTwelve).

Philip Golub's Loop 7 (2025) uses two pianos retuned to play in 22edo.

Microtonal music with more than two pianos

• Georg Friedrich Haas: Limited Approximations (2010) for orchestra and 6 pianos tuned to 1/12th tones (72edo
• Taylor Brook: Virtutes Occultae (2017) for "six physically modeled virtual pianos, each with a unique tuning in an extended 11-limit just intonation

Custom-built pianos

Some pianos with multiple manuals have been made for playing quarter-tone music. The table below, adapted from the Grove Dictionary of Musical Instruments, shows some of them.

Inventor/builder	Date	Manuals
G.A. Behrens-Senegalden (Berlin)	1892	2
Ivan Wyschnegradsky (Paris), built by Pleyel	1922	2
Alois Hába (Berlin), Ivan Wyschnegradsky, built by Grotrian Steinweg	1923-4	3
Moritz Stoehr (New York)	1924	2
Alois Hába (Prague), built by Förster	1924	2
Ivan Wyschnegradsky, built by Otto Pappe	1924	3?
Alois Hába, built by Förster	1925-9	3
Hans Barth (New York), built by George L. Weitz of Baldwin	1928	2
Ivan Wyschnegradsky, built by Förster	1928-9	3

There are some videos of Steve Cohn playing a Förster three-manual quarter-tone piano available on YouTube.

Julián Carrillo had pianos constructed in a range of tunings from 1/3-tones to 1/16-tones. These pianos metamorfoseadores, also known as Carrillo pianos, used conventional piano keyboards, so the range decreases as the divisions of the tuning get smaller.

Michael Harrison's harmonic piano plays a 24-note just scale and can be heard on From Ancient Worlds (1992).

Exciters for strings

By using some device to excite harmonics of the piano strings, it can be used to play notes higher up the harmonic series. For example, the magnetic resonator piano uses electromagnets to excite the strings. This can be heard on Xenia Pestova Bennett's Atomic Legacies (2020).

Further reading

Helmholtz discusses the acoustics of pianos in On the Sensations of Tone.

Owen H. Jorgensen's Tuning discusses historical temperaments used on the piano.

Ivor Darreg's 1967 essay Shall We Improve The Piano? addresses head-on a number of issues faced by music-makers wanting to use acoustic pianos.

See also

• Fluid piano