Piano
The piano is a keyboard instrument that produces sound when its keys are depressed, through engagement of an action whose hammers strike strings. Most pianos have a row of 88 black and white keys, representing each note of the chromatic scale as they repeat throughout the keyboard's span of seven and a quarter octaves. There are 52 white keys, known as “naturals”, and 36 black keys, known as “sharps”. The naturals repeat a pattern of whole steps and half steps unique to any given starting note. These patterns define a diatonic scale. The 36 sharps repeat a pattern of whole steps and minor thirds, which defines a pentatonic scale.
This article is about the musical instrument. For the musical dynamic, see Piano (dynamic). For other uses, see Piano (disambiguation).Keyboard instrument
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(Simple chordophone with keyboard sounded by hammers)
Early 18th century
We commonly think of the white notes as outlining the C-Major scale, but this is happenstance. Major scales are always composed of notes that ascend, from any given starting key (whether black or white), in this order: whole step, whole step, half step, whole step, whole step, whole step, and half step. It just happens that when we begin on a ‘C’, this pattern exists entirely on the white notes.
The black keys are raised above the naturals, are narrower and sit within a cutout in the back two-thirds of the naturals, which allows the keyboard to include the chromatic scale within a space that is manageable by the hand.
There are two main types of piano: the grand piano and the upright piano. The grand piano offers better sound and more precise key control, making it the preferred choice when space and budget allow. The grand piano is also considered a necessity in venues hosting skilled pianists. The upright piano is more commonly used due to its smaller size and lower cost.
When a key is depressed, the strings inside are struck by felt-coated wooden hammers. The vibrations are transmitted through a bridge to a soundboard that amplifies the sound by coupling the acoustic energy to the air. When the key is released, a damper stops the string's vibration, ending the sound. Most notes have three strings, except for the bass, which graduates from one to two. Notes can be sustained when the keys are released by the use of pedals at the base of the instrument, which lift the dampers off the strings. The sustain pedal allows pianists to connect and overlay sound, and achieve expressive and colorful sonority.
In the nineteenth century, influenced by Romantic music trends, the fortepiano adopted changes such as using the cast iron frame (which allowed much greater string tensions), and aliquot stringing which gave grand pianos a more powerful sound, a longer sustain, and a richer tone. Later in the century, as the piano became more common, it allowed families to listen to a newly published musical piece by having a family member play a simplified version.
The piano is widely employed in classical, jazz, traditional and popular music for solo and ensemble performances, accompaniment, and for composing, songwriting and rehearsals. Despite its weight and cost, the piano's versatility, extensive training of musicians, and widespread availability in venues, schools, and rehearsal spaces have made it a familiar instrument in the Western world.
Broadwood square action
Erard square action
When the key is struck, a chain reaction occurs to produce the sound. First, the key raises the "wippen" mechanism, which forces the jack against the hammer roller (or knuckle). The hammer roller then lifts the lever carrying the hammer. The key also raises the damper; and immediately after the hammer strikes the wire it falls back, allowing the wire to resonate and thus produce sound. When the key is released the damper falls back onto the strings, stopping the wire from vibrating, and thus stopping the sound.[45] The vibrating piano strings themselves are not very loud, but their vibrations are transmitted to a large soundboard that moves air and thus converts the energy to sound. The irregular shape and off-center placement of the bridge ensure that the soundboard vibrates strongly at all frequencies.[46] The raised damper allows the note to sound until the key (or sustain pedal) is released.
There are three factors that influence the pitch of a vibrating wire.
A vibrating wire subdivides itself into many parts vibrating at the same time. Each part produces a pitch of its own, called a partial. A vibrating string has one fundamental and a series of partials. The purest combination of two pitches is when one is double the frequency of the other.[47]
For a repeating wave, the velocity v equals the wavelength λ times the frequency f,
On the piano string, waves reflect from both ends. The superposition of reflecting waves results in a standing wave pattern, but only for wavelengths λ = 2L, L, 2L/3, L/2, ... = 2L/n, where L is the length of the string. Therefore, the only frequencies produced on a single string are f = nv/2L. Timbre is largely determined by the content of these harmonics. Different instruments have different harmonic content for the same pitch. A real string vibrates at harmonics that are not perfect multiples of the fundamental. This results in a little inharmonicity, which gives richness to the tone but causes significant tuning challenges throughout the compass of the instrument.[46]
Striking the piano key with greater velocity increases the amplitude of the waves and therefore the volume. From pianissimo (pp) to fortissimo (ff) the hammer velocity changes by almost a factor of a hundred. The hammer contact time with the string shortens from 4 milliseconds at pp to less than 2 ms at ff.[46] If two wires adjusted to the same pitch are struck at the same time, the sound produced by one reinforces the other, and a louder combined sound of shorter duration is produced. If one wire vibrates out of synchronization with the other, they subtract from each other and produce a softer tone of longer duration.[48]