The main difference between electronic keyboards and acoustic keyboards is that the sound created does not come from the physical movement of a string (piano) or a bellows forcing air through a pipe (organ). With an acoustic piano, depressing a key causes a hammer to drop down and strike one or more strings. These strings begin to vibrate and set the surrounding air into motion, creating sound waves heard by our ears and interpreted by the brain.

The sound of an electronic keyboard comes from a continuously changing electrical signal (analog) or a stream of numbers generated by a microprocessor (digital). The electrical signal of analog instruments, after a variety of manipulations, is heard through loud speakers which convert the changes in electrical polarity to air movement, resulting in sound. Digital instruments work in a similar way, but the stream of numbers must first be converted into a continuous electrical signal by an internal component called a digital-to-analog converter (DAC). The signal is then routed to a loudspeaker.

There are several types of electronic keyboards which are used for different purposes. The intended purpose will influence the choice of electronic keyboard. Some general things to consider when purchasing an electronic keyboard include touch-sensitivity (does the keyboard play louder when struck harder similar to an acoustic piano?), pressure sensing and aftertouch, or the ability to control the sound by pressing harder on keys after they are depressed and by how quickly the key is released.

The size of the keys should be considered. Are they mini keys, organ-style or full-size keys, or weighted keys? Mini keys are usually found on keyboards designed for the home market or for keyboard instruction to children in the elementary grades. How many octaves are needed... three or five? This will depend on if the instrument will be used for performance or instruction.

Can the keyboard instrument connect to a computer? To do so, it must be MIDI-compatible, with MIDI IN and MIDI OUT connectors on the back panel. MIDI (Musical Instrument Digital Interface) was created to standardize the transmission of information among electronic instruments made by the different electronics manufacturers. General MIDI is an attempt to standardize the locations of sounds for all keyboards, regardless of the manufacturer or model by assigning specific numbers to specific sounds. For example, sound number 1 will always be a piano. This makes it easier to find instrument sounds on all General MIDI keyboards. General MIDI is necessary for use with software and prerecorded sequences used on a computer. 

How many voices can the instrument sound at one time? Most keyboards are polyphonic, with 16-32 voice capability. This feature is more important for use with a sequencer or computer than performance, as human hands cannot play more than eight-ten notes at time. Is the keyboard multi-timbral or capable of producing more than one timbre at a time? This feature is important when recording and playing back music with a sequencer or computer.

Following is a list of the different electronic keyboard categories and the "key" features of each to help you decide which one might work best for you.

Digital Pianos

Digital pianos attempt to combine realistic piano action, realistic piano sound samples, and a full size keyboard of 76 or 88 keys with the control and convenience of an electronic instrument. They do this by playing back digital recordings or "samples" of acoustic piano sounds. Digital pianos concentrate on piano sounds with a limited number of other sounds. Most common of these other sounds are vibes, organ, harpsichord, and strings. Some digital pianos allow the player to layer sounds, playing more than one timbre at a time.

Like acoustic pianos, digital pianos are touch sensitive. They respond to touch so that the harder a key is pressed, the louder it sounds. Many digital pianos have weighted keyboards where weights are inserted inside the keys to give the same feel as an acoustic piano. Hammer action keys simulate the weight of an acoustic piano. Weighted or semi-weighted action keys have a heavier action than a synthesizer, but are not as heavy as hammer action. Like acoustic pianos, digital pianos have a sustain pedal, and some models have sostenuto and soft pedals as well. Digital pianos usually have from two to three pedals.

Digital pianos are less expensive than acoustic pianos, and they take up less space. A digital piano takes up more space than a synthesizer but is smaller than an acoustic spinet piano. Many digital pianos have speakers built in to them. The headphone jack allows for the use of headphones and sound privacy while practicing either in a piano lab or small private residence. Using headphones allows one to practice at any hour. Another plus, digital pianos never need tuning.

Some models include disk drives for playing back orchestral accompaniments and for recording performances. Most modern digital pianos have audio outs for plugging into larger sound systems and MIDI In and Out jacks for connecting to a computer or other MIDI device. USB connectors that bypass MIDI interfaces are becoming more common. Some models have audio input jacks that allow external synthesizer modules or computer audio to run through the internal speakers. A digital piano with multi-timbral banks of synthesizer sounds greatly expands its usefulness as a sound source for MIDI sequencing or as an electronic ensemble instrument. Digital pianos with synthesizer sounds often include a General MIDI sound bank, making it easier to use with accompaniment software and theory programs, as well as electronic ensemble arrangements that utilize General MIDI sounds. Most digital pianos do not have expressive controls such as pitch bend, modulation, and aftertouch, though some may respond to MIDI commands for expressive playback.

Digital pianos are often used for class piano labs, private piano studios, and home use. Since digital pianos replicate acoustic pianos, they are ideal for labs that are used for piano instruction. Digital pianos are the best choice for a classroom or studio situation that requires a high quality piano sound and action, and not necessarily easy portability. If the digital piano will not be used for true piano performance, the expressive advantages of hammers and pedals might be lost on beginners or general music students. Portable keyboards may be used instead for teaching basic keyboard skills, music theory, composition and arranging, whether in a lab or as an individual workstation.

Portable Keyboards

Portable keyboards are the least expensive type of electronic keyboard. They are compact, lightweight, and easy to transport. They can be set on a table top, desk, or keyboard stand. They are designed for the home or nontechnical user, and are easy and fun to use. Since the speakers are built in, an external sound system is not necessary. Portable keyboards often include dozens of high-quality sampled sounds that were digitally recorded, and can be selected with the push of a button. These sampled sounds include pianos, organs, and synthesizers, as well as string, woodwind, and brass instruments, drums, and special effects. Many portable keyboards also have auto-chord or auto-arranging features which create automatic harmonies and rhythms. Some allow you to record and play back your performance. Many department stores, electronics stores, music stores, and mail order catalogs carry portable electronic keyboards.

"Intelligent keyboards" are portable electronic keyboards with many advanced features and are designed for professional use. These instruments produce accompaniments, rhythms, and patterns that are professional sounding. Intelligent keyboards are more expensive than other portable keyboards because of the number of built-in features.

"Programmable keyboards" are best for live performances by solo artists, bands, orchestras, jazz ensembles, choruses, or electronic keyboard ensembles. They do not come with speakers built in, and are designed to be amplified using external equipment such as a keyboard amplifier or a sound system. Like other electronic keyboards, programmable keyboards come with a set of preset, factory-installed sounds. They can alter and create new sounds, and they can be identified by the type of display, usually a window showing numbers and parameters. Programmable keyboards have very good sound quality as they are used for performance. As with all electronic keyboards, a higher price tag means higher sound quality.

Electronic Organs

Electronic organs are designed to sound like traditional pipe, reed, and tone wheel organs. Most electronic organs also have the same types of features and controls as traditional organs, such as stops, foot pedals, and draw bars, as well as auto-arrangers, rhythm accompaniments, and built-in speakers. Some even simulate rotary speakers. Electronic organs are smaller, less expensive, and less bulky than traditional organs, making them very popular in the family and home markets.

Synthesizers and Samplers

Synthesizers and samplers are at the cutting edge of electronic keyboard technology. Synthesizers come in many varieties. Some play back digital recordings known as "wavetables" or "samples" of real sounds. Others allow you to construct interesting and unique electronic sounds from scratch. Samplers are like digital tape recorders, allowing you to record any original sound in memory and then play it back from a keyboard. Sampling does not attempt to recreate sounds electronically. Samples are actually digital recordings of sounds. Sample players such as electronic keyboards only play back samples of sounds. A sampler can play back as well as record samples of sounds. Using wheels, pedals, sliders, and footswitches, you can add expressive control to the sounds you create. There are many large libraries of preprogrammed sounds available.

Synthesizers come in 61, 63, 76, and 88-key versions, and in a variety of price ranges. Synthesizer keyboards usually have a lighter touch than a digital piano keyboard. They often have built-in sounds and expressive performance controls such as pitch bend, modulation, and aftertouch. These controls are important for effective MIDI sequencing and ensemble and solo performance. Synthesizers with velocity sensitivity respond to how hard the key is played. The harder the key is pressed, the louder it sounds. The pitch bend wheel gives you the ability to raise or lower the pitch of the keyboard 1/2 step. Most synthesizers have a jack in the back that allows you to plug in a sustain pedal. This is useful if you are going to perform with the instrument. Foot pedals can also control volume and a variety of effects. Pedals usually are not included with synthesizer keyboards and must be purchased separately. Other necessary accessories are keyboard stands or a desk surface, amplifiers for live performance, and headphones.

Most synthesizers and samplers are multi-timbral, meaning they can play back several different sounds simultaneously. When used with music software or onboard sequencers, they can allow you to hear entire orchestrations of your music. All synthesizers have a limitation on the number of notes that can be played at the same time. The polyphony of an instrument includes notes being held by the sustain pedal, and can range anywhere from 8 to 64 notes.

Some synthesizers and samplers do not have a keyboard. These "sound modules" are standalone boxes that contain a collection of sounds in memory which are triggered remotely from a computer or a connected keyboard via MIDI. Most sound modules are also General MIDI-compatible so that they can be used to play back Standard MIDI Files.

Workstations

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

Keyboard Controllers

A keyboard controller is a MIDI keyboard without sounds that triggers the sounds built into a computer. Most current computers have sounds built into them, and by triggering those sounds with a keyboard controller, you have a keyboard synthesizer. Keyboard controllers come in 37, 49, 61, 76, and 88-key versions. The most common are the ones with 49 or 61 keys. Keyboard controllers are less expensive than synthesizers. The disadvantage is that the sounds built into most computers are not as good as those of most synthesizers. However, the built-in computer sounds work fine for instructional courseware. Keyboard controllers work well in computer labs as they are an extension of the computer.

Keyboard-Related Web Sites

See my Keyboard Chops article "Piano/Keyboard/Organ Web Sites" on this site for links to keyboard manufacturers, or do search on the Internet. Visiting keyboard manufacturer Web sites is a great way to stay current on new gear and product upgrades.

Happy keyboarding!