For considerably less money than you shell out for an acoustic keyboard, also known as a piano, you can own a digital keyboard capable of sounding like just about any other instrument on the planet (including an acoustic keyboard).
Instead of vibrating strings to make sounds, most keyboards of the electronic variety produce sound by one of the following ways:
Generating sound waves (the old-fashioned way)
Producing sampled sounds (the newfangled way)
These sounds are then amplified, sending vibrations to your eardrum and thus causing you to hear the sound.
Synthesizers
Like bakers, dancers, and burglars, synthesizers derive their name from the work they perform — they synthesize sound. First they use an oscillator to generate sound waves electronically. Then, in the synthesis part, they alter the shape, frequency, and volume of the sound waves and combine them to create different sounds. Synthesizers can create goofy hums and buzzes as well as imitate virtually any instrument imaginable. A programmable synthesizer, commonly known in hip music-industry lingo as a synth, lets the programmer (that’s you) shape and modify the sound waves with buttons, knobs, switches, and sliders. You can make your synthesizer sound like the entire Vienna Philharmonic is in your living room!
Digital keyboards
Digital keyboards work with sampled sounds. Sampled sounds are made by digitally recording discrete audio samples of an instrument (or any other sound) and storing them in the brain of the keyboard. When you choose a sound on the keyboard’s display panel and press a key on a digital keyboard, you access the sampled sound and through amplification play the digital information out into the audible realm.
As you can imagine, the quality of digital sound depends on the quality of the sample, and this is one of the features that distinguish the many digital keyboards. Depending on the model and price, digital keyboards come with a variety of features to simulate the experience of playing a real piano or organ. They also help you to augment the experience with lots of other fun options, like recording and editing your own playing, accessing other instrument sounds at the touch of a button, and connecting to other keyboards or your computer.
Many digital keyboards feature a bonus auto-accompaniment feature. With the push of a single button, you can have a nonstop-always-on-the-beat drum and bass line accompanying you. (Bossa nova, anyone?)
Perhaps the biggest downside of a digital keyboard is the sound and touch compared to an acoustic piano. Some digital keyboards don’t respond to your touch no matter how fast or slowly you press a key; Touch-sensitive keyboards produce louder or softer sounds depending on the speed of your touch. A keyboard with weighted keys is closest in feel to an acoustic piano.
Given their ability to put realistic samples of other instruments at your fingertips, digital keyboards are the next generation of the synthesizer.