A digital piano is an electronic keyboard that emulates the sound and the feel of a genuine acoustic piano. It can be differentiated from its precursor instrument – the “synthesizer” – which uses electronically produced sound waves to create specifically electronic sounds.
The first digital piano commercially available was produced by Yamaha in 1983. The Clavinova YP-40 was the most notable of the releases. More of an extension of the synthesizers of the 1970s, the sounds were electronically produced using Frequency Modulation, rather than sampling technology which is used by all digital pianos today. 
Frequency Modulation synthesis (more commonly referred to as simply “FM”) works by modulating (or changing) the frequency of an electronically produced sound wave. This results in a wide variety of tone, dependent upon the changes in frequency and a combination of other waves. 
A sample, on the other hand, is a short digital recording that can be triggered via a MIDI instrument, such as a piano-style keyboard. 
A modern digital piano has a large bank of short digital recordings (samples) that are triggered by hitting the keys of the keyboard. Most modern digital pianos are capable of reproducing touch-sensitive play (see later).
Modern digital pianos contain samples taken from a variety of genuine grand (and upright) pianos, recorded at high quality. Most digital pianos offer more than one piano sound, as well as a variety of other instrumental sounds such as electric piano, organs and strings.
But it’s not just the sound you should look out for when choosing a digital piano. The build quality is massively important and can truly affect your experience of playing.
It’s important to understand some of the mechanics of the acoustic instrument when exploring the features of the digital piano, so we’ll be focusing on the relevant mechanisms in this article.
The digital piano was developed to bring the experience of a genuine piano to a versatile, compact unit, so understanding the internal workings of the digital piano (and how it relates to the acoustic instrument) can help you choose a digital piano that feels like the real thing.
The most popular manufacturers of digital pianos are Yamaha, Roland, Kawai and Casio.
The pianoforte is a percussion instrument
We usually associate percussion with instruments that you hit, strike, bang or purposely collide, either with a stick, a beater, a key or the hand. Examples of commonly recognized percussions instruments are drums, timpani (aka kettle drum), cymbals, gongs, glockenspiels, xylophones and tambourines.
The piano is played by pressing the (usually) white and black keys on the keyboard. When a key is pressed, it triggers a chain of events that ends with a felt-coated hammer, striking a string (or strings). It is this “hitting” action that classifies the piano as a percussion instrument.
The acoustic piano usually has three strings per note to create a fuller tone – the hammer hits all three strings. 
Digital pianos don’t usually have strings, but they do have the same keyboard interface as the acoustic instrument – at least, on the surface. Rather than hitting a string, the depression of the key results in contact with an electronic sensor which triggers the note. Sensors can often detect more than just “on” and “off” and many can respond to the intensity of the key press. 
The full name of the instrument widely referred to as the “piano” is actually “pianoforte”. Pianoforte is a conjugation of two Italian words, referring to the dynamics of musical play – “piano” meaning “soft” and “forte” meaning loud. The pianoforte, therefore, is capable of playing both quietly (by pressing the key softly) and loud (by pressing the key with harder force). All digital pianos also have this ability. 
THE BOTTOM LINE –
The piano is a percussion instrument that is capable of playing a wide range of dynamics (dynamics are variations in the volume of the music) – more than that of the guitar.
The sound of a piano note is achieved by a hammer hitting a string (or strings). The keys of a digital pianos connect with a sensor that triggers an audio sample.
Digital pianos can often recognize the velocity of the key press and respond with either loud or soft playback of the audio sample.
Never buy a digital piano until you’ve tried it out. The instrument should be capable of a wide array of dynamic responses, including accurate soft and loud play.
The piano keyboard is the musician’s interface, providing control over the instrument. A full-sized piano has 88 keys, arranged in a regular sequence of white and black keys. A digital piano can come in a variety of sizes, but if you’re looking for an instrument that looks and feels like a genuine piano, you should demand 88, full-sized, weighted keys. The full-sized piano keyboard spans 8 octaves.
The keys of an acoustic piano are traditionally made from wood, and laminated with either an ivory surface (for the white keys) or an ebony surface (for the black keys). The keys of digital pianos are usually made from plastic, although some higher-end models use real piano keys.
The black keys sit in between and slightly raised from the white keys. Navigation around the keyboard is made possible from recognizing the repeated sequence of black keys, which are grouped in 2s and 3s, respectively. 
A sequence of 2 black adjacent notes is followed by two adjacent white notes, followed by 3 black notes, followed by another 2 adjacent white notes. This arrangement is repeated throughout the entire keyboard.
There are 7 notes in the music “alphabet” – A, B, C, D, E, F and G, which repeat across the entire keyboard. A full octave is 8 notes apart – C to the next C, for example.
THE BOTTOM LINE –
A full-sized piano has 88 keys which are a combination of white and black notes. Navigation of the keyboard is afforded by the grouping of the black notes, which are in 2s and 3rd, regularly across the entire span of the keyboard. Digital pianos use exactly the same arrangement of keys as acoustic pianos.
When looking to buy a digital piano, it’s advisable to go for an 88 key model. Keyboards come in a variety of ranges from just 25-, 49- or 61-key. The larger the keyboard, the less portable it becomes, so if you’re looking for a digital piano that’s going to stay in one place, 88 keys is best.
When you depress a note on an acoustic piano, there’s a mechanical chain of events that ends with a hammer that hits a string. This sequence of arms and levers gives the piano a weight that musicians have come to expect from the piano playing experience.
A piano key of a grand piano operates a little like a see-saw. When you depress the key, it pivots the arm in the centre, raising a hammer attached to the other end of the wooden arm which strikes the string.
The part of the key that you can commonly see is just one section of the hammered arm.
Traditionally, the keys at the bottom end of the piano playing the “low” notes (the left hand side of the keyboard) have longer wooden arms than the “top” notes (played on the right hand side of the keyboard) which have shorter arms. 
This difference in key arm lengths adds a different physical weight to the keys. The bottom keys of a grand piano are “heavier” under the fingers because they have longer arms than the top keys.
Many digital pianos have weighted keys, using various mechanical means to reproduce the sensation of weight. Some of the higher-end models have a “Graded Hammer Action” which emulates the traditional grand piano by weighting the keys more heavily at the bottom end of the keyboard and more lightly at the top.
If you’re looking for a digital piano with a realistic, pianistic keyboard, you should look for a model that has a “Graded Hammer Action”.
THE BOTTOM LINE
The keys of acoustic pianos feel heavier at the bottom end (the left hand side) and lighter at the top end of the keyboard (the right hand side). This is due to the length of the wooden arm that pivots, resulting in the hammer of the key hitting the string or strings.
Many digital pianos emulate this keyboard weighting with a system called “Graded Hammer Action”.
Decent weighting of the keys of a digital piano is essential. If you learn on a digital piano, you need to develop the muscle-memory required to play dynamic music, which you will only learn accurately if the keyboard feels like an acoustic piano to play.
The Hammer Mechanism
Although most digital pianos don’t have the same hammer mechanism as an acoustic piano, an understanding of the mechanics (and how they’re emulated with digital instruments) will help you to decide which piano is the best choice for you.
There are 5 essential elements to a piano key mechanism – the key, the fulcrum, the hammer, the damper and the string.
The key is the part of the mechanism that you can see, covered in ebony and ivory (or a more ethical alternative). The resting position for the key is “up”. At resting position the hammer is away from the string and the damper rests on the string to stop the string from resonating.
The resting position is determined by the position of the fulcrum – effectively it sits closer to the key than to the damper, making the hammer and damper end of the key-arm longer (and thus heavier). This is where the “weight” of the key comes from.
When you press the key down, the fulcrum pivots the hammer arm upwards, making the hammer hit the string. At the same time, the damper lifts and stays lifted allowing the note to sustain and the strings to continue to resonate until the point at which the key is released, making the damper return to its resting position, sitting upon the string and stopping the resonation. 
This hammer action is emulated in many ways with digital pianos. Digital pianos are generally smaller than acoustic pianos and, therefore, don’t have the internal space (or need) for the full key mechanism. The big manufacturers have developed unique methods of approximating the mechanics of a real piano, but have condensed the whole workings in half of the physical space.
For example, Kawai has condensed the entire workings of the piano mechanism into the space below the key. When you release the key of an acoustic piano, there’s a light “bounce” (known as “key-off bounce”) as the mechanics of the key return to equilibrium. Kawai’s Responsive Hammer Action III device emulates the full mechanical experience of playing a real piano key, including the key-off “bounce”. 
Cheaper digital pianos emulate the hammer mechanism with a key, a weight and a spring. The problem with a “sprung” key is that it bounces back into the resting position too harshly, without a realistic key-off bounce.
When looking to choose a digital piano, it’s useful to research the hammer response – many music shops provide a small display model of the mechanism. However, the real proof of the pudding is in the playing.
THE BOTTOM LINE –
If you’re familiar with how an acoustic piano feels to play, look for a keyboard that realistically emulates that. Digital pianos at the higher end have become incredibly realistic – if you have a budget of over $1500, you should expect a great keyboard build as standard.
If possible, avoid buying a digital piano with “sprung” keys – the play feel will be unrealistic. Although digital pianos are triggering digital sounds, the more mechanical the actual keyboard build, the more realistic a playing experience you’ll get.
Escapement is part of the mechanical hammer action of an acoustic piano. You’re likely to notice the term in the specification list of many digital pianos.
As we know, when you press a key on an acoustic piano, it forces the hammer to hit the string. But the hammer immediately moves away from the string, even if you keep holding down the key, otherwise the hammer would remain on the string and dampen the sound. You would normally hold the key down if you are playing a long note.
It’s the escapement that drops the hammer away from the string so that the note can sustain.
You can feel the point at which the escapement triggers by playing a key really softly on an acoustic instrument. You’ll feel a “bump” about three quarters of the way down – this is the escapement mechanism.
The escapement allows the note to sustain by moving the hammer away from the key. However, the note can’t be played again until the key has been fully released (or release just above the escapement).
This is problematic if you’re playing rapidly repeated notes – especially if you’re playing them softly. Unless you play “above the escapement” you’ll have missed notes.
With an acoustic piano, you learn where the escapement “bump” occurs and develop the technique of playing “above the escapement” to avoid this mechanical misfiring.
With a digital piano, of course, there are usually no strings or an actual hammer. However, many of the higher range digital pianos include this escapement “bump” to emulate the feel of a real piano keyboard. 
THE BOTTOM LINE –
Escapement is a mechanism that you often find in high-end digital pianos. It emulates the “escapement bump” present in the mechanical workings of an acoustic piano. Playing soft and fast can be difficult on an acoustic piano because the escapement can prevent quickly repeated notes, unless the player learns to play “above the escapement”.
If you learn on a digital piano without escapement, you’ll experience problems when you sit at an acoustic instrument, unless you learn to play above the escapement.
Escapement in a digital piano provides a more authentic playing experience, so if you’re looking for a digital instrument that’s as close to the real article as you can get, look for a digital piano with an escapement mechanism.
Plastic vs Wooden keys
Acoustic pianos have wooden keys. This provides weight to the key mechanism. Most digital pianos have plastic keys. However, more recently, some of the high-end model ranges have started to re-introduce wooden keys. Some manufacturers boast “real piano keys” as a selling point.
But does it make any difference?
To cut the argument short – yes, it does. It certainly adds to the price!
Early digital pianos had purely plastic, often hollow keys, that afforded very little actual “weight” to the body of the key. Any physical weight added to the key-feel was via a spring mechanism or a weight attached to the plastic key. Whilst being completely acceptable, hollow plastic keys often lack the feel of an acoustic piano. 
Most modern, high-end piano manufacturers have moved away from the basic, hollow plastic key, developing new surface feels (sometimes referred to as “Ivory feel”) and weightier plastics that aim to emulate or even improve upon the acoustic piano feel. Matte-finish keys are commonly seen in some of the higher-end models.
Matte-finish keys have been developed to prevent finger slippage, and to absorb finger perspiration, providing a better connection between finger and key. This is an innovation found only in digital pianos – acoustic piano keys tend to have a glossy finish, whether they’re ebony and ivory or an alternative wooden build. 
Some digital pianos in the top price bracket have genuine, wooden piano keys. If you have a high budget and want an instrument close to the real thing, look for wooden keys.
THE BOTTOM LINE –
Plastic keys come as standard with most digital pianos. If you have a higher budget, you can look for “Ivory feel” keys. These are usually fully plastic, composite keys that have a weightier feel than a hollow plastic key, which was more common with early digital pianos.
Some digital piano manufacturers have started to reintroduce “real piano keys”. These, obviously, have the most convincing piano feel but come at a considerable price premium.
The foot pedals
There are usually two foot pedals with a standard upright acoustic piano, and three foot pedals with a standard grand piano. The two pedals on an upright operate the una corda and damper operations.
Digital pianos, originally, had just two pedals. More recent models, however, have a third (sostenuto) foot pedal, just like an acoustic grand.
To understand what each pedal does, it’s useful to understand the role each pedal plays with an acoustic piano.
The una corda pedal is situated on the left hand side of the pedal configuration.
Under normal conditions, the hammer hits three strings which creates a fuller, louder tone. However, when the una corda pedal is depressed, the hammers on a grand piano move to the right, making the hammers hit just two of the strings (or more traditionally, one of the strings (hence “una corda”).
The instrument, as such, produces a quieter, softer tone. Hence, the una corda pedal is more commonly referred to as the “soft” pedal.
The una corda pedal plays a slightly different role with an acoustic upright piano – rather than moving the hammers to the right, the una corda pedal moves the hammers closer to the string, thus reducing the distance the hammer can travel towards the key, resulting in a softer note.
The damper (or sustain) pedal is on the right hand side of the pedal configuration and is the most commonly used of all the foot pedals.
When a key is pressed, the hammer hits the string and the “damper” (which usually sits on the string) raises, allowing the string to resonate. When the piano key is released, the damper returns to the string and prevents further resonation.
However, the damper pedal, when pressed, physically moves the damper away from all of the strings; thus permitting all of the strings to resonate whenever a key is played, resonating until the damper pedal is released or the sound has naturally decayed.
Playing the piano requires sensitive use of the damper pedal – over-use creates a “muddy” sound. There are various techniques associated with damper pedal play, including “half damper” which reduces the overall effect of the fully open damper. 
Acoustic pianos respond depending upon how far you press the damper foot pedal. A light press results in a half-sustain. Only some digital pianos are capable of this range of control – look for “damper control” in the list of specifications. 
When there are three foot pedals, the middle one is the “sostenuto” pedal. The pedal to the left is the una corda, and the pedal to the right is the damper. The sostenuto pedal is quite rarely used.
The “sostenuto” pedal operates in a similar way to the damper pedal, in that it releases the dampers from the strings. However, the sostenuto pedal lifts the damper from only the keys that are played at the time that the pedal was pressed. All following notes are played with the damper in the usual position. This creates sustain of the notes played whilst the pedal was pressed and a “staccato” effect for the following notes.
The term “Staccato” means short, detached. A staccato note is played quickly and the sound dampens immediately. 
Digital piano pedals
The pedals of a digital piano emulate the acoustic instrument. However, there is no damper inside a digital instrument. Changes in the production of the sound is made possible by triggering different samples, rather than any physical changes to internal resonance. 
With some digital pianos, the middle foot pedal can be assigned to different tasks, such as page turning for sheet music apps (on a computer tablet such as an iPad) or for changing instrumental voices.
THE BOTTOM LINE –
Most digital upright pianos have at least two foot pedals which operate an una corda (or soft) and a damper (or sustain) function.
Una corda (or the soft pedal) produces a quieter sound. The damper pedal allows the whole instrument to resonate until the pedal is released.
Some digital pianos have a sostenuto pedal, which is situated in the middle of the three pedals. Sostenuto is an effect that sustains some notes and dampens others.
The middle pedal can often be assigned to perform different tasks in a digital piano.
The construction of a digital upright piano
The digital upright piano consists of the keyboard unit (containing the keys, the circuitry and the speakers), attached to a permanent stand or housing unit.
The keyboard unit is permanently attached to a stand unit (although most can be temporarily detached). The stand unit usually consists of a pedal board, which includes at least two foot pedals and a speaker unit, often containing multiple speakers.
A digital piano is often capable of producing a variety of sampled and electronic “voices”. Most digital pianos have more than one piano sound, with a variety of room resonance settings that help transport the player to the large concert hall.
Other voices commonly found with digital pianos include electric pianos (Fender Rhodes sounds), organs (such as jazz and church organs) and strings.
A keyboard with many voices isn’t necessarily better than one with few. If you are going to use your digital piano purely for playing piano voices, it’s worth focusing on the instruments that reproduce the best piano tone, rather than being attracted by the slightly “gimmicky” additional voices that you are unlikely to use. 
Most digital pianos allow the user to connect at least one pair of headphones, providing “silent” operation of the instrument and allowing the player to perform without disturbing other people in the immediate vicinity. This is one of the most popular features of the digital piano over the noisy acoustic instrument.
Many modern digital pianos have two headphone outputs, which is good for piano lessons. 
Digital upright pianos have a user interface that allow the user to choose between the various features of the piano, as well as control the different on-board voices. User interfaces range widely in quality and mode. Some top-end digital pianos have LCD navigation displays that provide quick access to the piano’s main editable functions. 
Some lower-priced digital pianos have very simple user-interfaces that have limited functionality.
Most digital upright and stage pianos have volume controls that adjust the decibel output of the speakers.
THE BOTTOM LINE –
Digital upright pianos are furniture-style units that contain the keyboard unit and a permanent stand that houses the foot-pedals and the speakers of the instrument.
The user interface of the digital piano allows you to control which instrumental voice plays, as well as providing many editable functions that dictate changes in the way that the instrument sounds.
A stage piano is a digital piano that comes as a single, portable unit. It has no built-in stand or housing unit and has no native foot pedals attached, although most come with a detachable damper pedal as a minimum. A collapsable X-Frame stand is most commonly used for a stage piano.
Stage pianos usually contain the vast majority of the operations capable with a digital upright. They are popular with professional, touring musicians because they are designed to be easily transported. They usually have less complex user interfaces (digital screens) than digital uprights.
Most modern stage pianos have an internal speaker system, although some (usually older) models require external amplification via a PA system.
The keyboard build is likely to be similar or the same as digital upright pianos. However, stage pianos need to be relatively lighter in weight as they need to be transported, so sometimes have lighter internal components.
Stage pianos are generally cheaper to buy than digital upright pianos, but usually offer equivalent functionality. More stage pianos do have fixable stands as additional accessories, which are worth buying if you intend to keep your stage piano for home use. 
THE BOTTOM LINE –
A stage piano is a digital piano unit with no fixed stand, designed for portability. They’re popular with professional, touring musicians. They require additional foot-pedals – most come packaged with (at least) the damper pedal, as this is the most commonly used.
Stage pianos are generally cheaper to buy than digital uprights and have equivalent functionality. Most stage pianos have fixed stand units available as an optional accessory.
MIDI is a digital protocol developed during the early 1980s which facilitates the communication of electronic instruments. The term MIDI is an acronym for Musical Instrument Digital Interface.
MIDI, in itself, does not produce any sound – it is more accurately defined as a list of messages sent almost instantaneously between instruments (or recorded and stored for later reproduction). The messages are On / Off (1 / 0) commands – controlling Note on, Note off, Note/Pitch, Velocity, Pitchbend etc. These messages are sent by one instrument (or computer) and received by another which interprets those instructions using its internal component functionality.
MIDI information is transferred via a cable or through wireless means, such as Bluetooth. 
The first MIDI cables were 5 pin DIN cables, which had previously been used to transmit data and audio signals.  This connection protocol can only carry information in one direction, so with old MIDI instruments, there was a MIDI IN and a MIDI OUT (and occasionally MIDI THRU) sockets.
The Master device (sending the MIDI data) would use its MIDI OUT socket, which was connected to the MIDI IN of the receiving (or Slave) instrument.
In order for the Slave instrument to send data back to the Master device (often a sequencer), its MIDI OUT connection needed to be connected to the Master’s MIDI IN. 
More recently, USB cables have been used to transfer MIDI information between electronic instruments. A USB cable provides two way information, so only one cable is required as opposed to the two cables required with 5 pin DIN MIDI. This has been a major breakthrough in the ability for home computers to natively connect directly to electronic musical instruments. 
Bluetooth MIDI is the latest innovation in MIDI data transfer, opening up the music making functionality of mobile devices such as mobile phones and tablet computers. Bluetooth MIDI allows electronic musical instruments and interfaces to communicate wirelessly.
Not only does Bluetooth allow for data transfer, but can also allow for audio transfer. This is a real breakthrough for the mobile musician, allowing a mobile app (such as Cubase or Korg Gadget) to be controlled externally, transmitting the resulting audio signal through the external speakers of the receiving instrument. 
THE BOTTOM LINE –
MIDI is a digital language that allows musical instruments and music computer software to communicate. All digital pianos have some kind of MIDI interface, allowing the user to expand the capabilities of the instrument.
Instruments connect together via 5 pin DIN and / or USB cables, or wirelessly via Bluetooth.
Bluetooth has brought about a sea-change in how we connect appliances together and, for the music world, it has revolutionized how one instrument communicates with another. MIDI is a language of ones and zeros and doesn’t transfer audio, just data. However Bluetooth connection has changed all of that.
Now it is possible to wirelessly link your digital piano to one of the countless music-making apps available on Apple’s iOS platform. iOS is leading the way, by offering a wide array of music apps, with the likes of Steinberg and Korg heavily investing in the platform to present great, professional, mobile studio software such as Cubase and Gadget, amongst a wide expanse of others. 
iOS devices have much lower audio latency than Android devices, so for the present, music apps for Android mainly cater to the gaming market as opposed to the serious music-maker 
The big advantage with Bluetooth is that your device doesn’t just connect to your digital piano to communicate MIDI data, but transfers digital audio as well. The iOS device connects its audio output wirelessly to the internal speaker system on your digital piano. This holds amazing connectivity potential.
Some digital pianos have rather disappointing user interfaces, providing little by way of editing the play and sound parameters of the instrument. Some keyboards – the Kawai CN27, for example, is capable of some really detailed player customizability, but has only 6 buttons and a digital display that makes navigating the potential options impossible.
However, the CN27 has on-board Bluetooth capability which extends to a “Virtual Technician” iPad app, allowing the user the ability to change many digital parameters that affect both the piano playing experience and the sound produced by the instrument.
For example, it’s possible to change room sizes within the reverb settings, adjust foot-pedal noise, virtually raise or lower the piano lid to adjust the brightness of the overall sound, even affect tuning. 
More and more digital pianos are built with native Bluetooth capabilities. For those that aren’t, there’s usually a Bluetooth dongle that can be fitted to facilitate Bluetooth communication between devices.
THE BOTTOM LINE –
Bluetooth can transmit both audio and MIDI data, making it the future of wireless connectivity for electronic musical instruments. Many modern digital pianos have native Bluetooth capability, although there are dongles available that are compatible with the most recent modes if they don’t.
Bluetooth allows a digital piano to connect to music-making apps (principally on Apple’s iOS platform), potentially adding vast studio-making capabilities to your existing instrument.
There is a wide array of music-making apps available on Apple’s iOS platform, offering cutting edge music-production capabilities to your digital piano.
It also allows the user to control detailed parameters with “Virtual Technician” apps, for digital pianos that lack a detailed user interface.