The key factor that differentiates electronic keyboards from acoustic ones is that the sound they create is not derived from the physical movement of a string or a bellows forcing air through a pipe. In an acoustic piano, for example, the act of depressing a key causes a hammer to drop down and strike one or more strings, which then begin vibrating, in turn setting the surrounding air into motion. This back-and-forth movement of air is then received by sensitive mechanisms in our ears, and the resulting nerve impulses are interpreted by our brain as sound.

In contrast, the sound of an electronic keyboard begins its life either as a continuously changing electrical signal (if the instrument is analog) or as a microprocessor-generated stream of numbers (if the instrument is digital). In the case of analog instruments, the electrical signal, after being manipulated in a variety of ways, is finally routed to a loudspeaker, which has the task of converting the changes in electrical polarity to movement of air, resulting in a sound. Digital instruments work much the same way, only the stream of numbers has to first be converted into an equivalent continuous electrical signal; this is the function of an internal component called, appropriately enough, a digital-to-analog converter (or DAC for short). From there, it is routed to a loudspeaker in the usual way.

Within this broad definition, there are a number of different types of electronic keyboards. In this article, we'll describe the differences between the categories and highlight the key features of each.

Digital Pianos

Digital pianos combine the sound of an acoustic piano with the control and convenience of an electronic instrument. They do this by playing back digital recordings ("samples") of acoustic pianos (and, often, other sounds as well), triggering different notes as you play different keys. Like acoustic pianos, they respond to your touch so that the harder you play, the louder (and brighter) the note, and, like acoustic pianos, they provide a sustain pedal (some have sostenuto and soft pedals as well). Many digital pianos even have weighted keyboards so that they have the same kind of feel as their acoustic cousins. But digital pianos are much less expensive than acoustic pianos, take up less space, and never need tuning. Plus, using headphones, you can practice late into the night without disturbing your family or neighbors! Some models even include disk drives so that you can play back orchestral accompaniments and record your performances.

Electronic Organs

Electronic organs use modern technology to closely emulate the sounds of traditional pipe, reed, and tone wheel organs. Most also provide the same kinds of features and controls, such as stops, footpedals, and drawbars, as well as autoarrangers, rhythm accompaniments, and built-in speakers some even have rotary speaker simulation! However, all this is accomplished in a package that is a fraction of the size, bulk, and cost of a traditional organ, making the electronic organ a popular favorite for family enjoyment at home.

Synthesizers and Samplers

Synthesizers and samplers represent the cutting edge of electronic keyboards. Synthesizers come in lots of different varieties some play back digital recordings ("wavetables" or "samples") of real sounds, while others allow you to construct other-worldly electronic sounds from scratch. Samplers act like digital tape recorders, allowing you to record your own original sounds in memory and then play them back from a keyboard. Using wheels, pedals, sliders, and footswitches, you can add endless amounts of expressive control to the sounds you create, and there are also enormous libraries of preprogrammed sounds available.

In addition, most synths and samplers are "multitimbral," meaning that they can play back several different sounds at the same time. Used in conjunction with music software or onboard sequencers, they allow you to hear entire orchestrations of your music, including drum and percussion sounds.

Some synths and samplers don't even have a keyboard at all! These are known as "tone modules" standalone boxes that contain a collection of sounds in memory which are triggered remotely from a computer or a connected keyboard via MIDI (the Musical Instrument Digital Interface the standardized "language" of electronic instruments). Most tone modules are also General MIDI (GM)-compatible so that they can be used to play back the wide selection of Standard MIDI Files (SMF)s available on the Internet and through music distributors.

Workstations

The term "workstation" is generally applied to any synthesizer or sampler that includes drum and rhythm sounds in addition to standard instrument sounds, as well as an onboard sequencer and built-in effects such as reverb, delay, chorus, flanging, and phasing. They are, in effect, complete music studios that allow you to create entire orchestral compositions without the need for any additional equipment.

Portable Keyboards

As their name implies, portable keyboards are affordable, compact, lightweight, and easily transportable. They're also easy and fun to use -- and, since they have built-in speakers, no external sound system is required. In many ways, portable keyboards are the chameleons of the electronic keyboard world, since they often include dozens of high-quality sounds, including pianos, organs, and synths, as well as drums and special effects. Many portable keyboards also offer auto-arranging features and even allow you to record and play back your performances!