Electronic keyboard synthesizers have come a long way since their inception. Few people know that the first electronic synthesizer was invented in the late 1800s. This model was, of course, only a very rough precursor to the musical synthesizers of today. Modern synthesizers are capable of producing a variety of sounds by generating and combining signals of different frequencies. This process is called synthesis, and it can be divided into five distinct types: wavetable, physical modeling, digital, fingerboard and software (digital).
Wavetable synthesis uses an existing sound to create a digital recording, which is known as a sample. This recording can be replayed at a range of pitches. While other synthesis methods use oscillator circuits to produce repetitive electronic signals, wavetable synthesis uses sample playback. If an artist wants to change the musical tone of a passage, the speed of the playback is quickened or slowed accordingly. For instance, in order to alter the frequency of a sound one octave higher, it is played at double speed. Wavetable synthesis is used in certain digital music synthesizers to implement real-time additive synthesis and direct digital synthesis with minimum hardware.
Physical modeling synthesis uses a set of equations and algorithms to simulate the desired physical source of a sound. In order to generate a specific sound, an initial set of parameters is run through the physical simulation. Physical modeling is based on the concepts of acoustics and synthesis. The development of the Karplus-Strong algorithm and the increase in digital signal processor (DSP) power in the late 1980s allowed for the commercial implementations of modern synthesizer physical modeling.
Digital synthesis involves using a digital oscillator to generate a digital sample that corresponds to a sound pressure at a given sampling frequency. In most basic instances, the digital oscillator is modulated by a counter. For each generated sample, the counter is advanced by an amount determined by the frequency of the oscillator. The values are recorded by the oscillator's counter, mixed, processed and sent to a digital-to-analog converter. The resulting analog signal is then sent to an analog amplifier, which converts the signal to sound.
Fingerboard synthesis utilizes a ribbon controller, which is a user interface used to control the parameters of analog synthesizers. A ribbon controller is similar to the touchpad of a laptop computer in that it registers and translates the motion and position of the user's fingers. However, most ribbon controllers only register linear motion. Although it could hypothetically be used to alter and control any sound parameter, a ribbon controller is most commonly associated with pitch control or pitch bending.
Digital synthesis is possible on most modern, high-speed personal computers through a variety of available software. DSP algorithms are commonplace, and they allow for the creation of fairly accurate simulations of physical acoustic sources or electronic sound generators. Some commercial programs offer quite lavish and complex models of classic synthesizers. Other programs permit the user complete control of all aspects of digital music synthesis, although such programs can be expensive and difficult to use.
