Effects units
Effects units are electronic devices that affect the sound of an electric or electronic instrument or other audio source. Effects can be used in "real time", during a live performance (typically an electric guitar or electric bass), or in post-production, with recorded material. To use an effect in a live performance, the effect is plugged in to the electrical signal path of the instrument. In a post-production setting, the source's auxiliary output is patched into the effect. Effects can also be used on other instruments or sound sources, like the Rhodes electric piano, synths or even the human voice. While some effect units "color" the sound in a subtle way, others transform the sound in a dramatic fashion.
An effects unit consists of analog or digital circuitry which processes audio signals. In some cases, effects processing circuitry is similar to that found in music synthesizers, as it may include active and passive filters, envelope followers or envelope modifiers, wave-shaping circuits, voltage-controlled oscillators, or digital delays.
Effects units come in several formats, the most common of which are the stomp-box and the rack-mount unit. A "stomp box" is a small metal or plastic box containing the circuitry which is placed on the floor in front of the musician and connected in line with the patch cord connected to the instrument. The box is typically controlled by one or more foot-pedal on-off switches and typically contains only one or two effects.
A rack-mount effects unit may contain the identical electronic circuit, but is mounted in a standard 19" equipment rack. Usually, however, rack-mount effects units contain several different types of effects. They are typically controlled by knobs or switches on the front panel, and often by a MIDI digital control interface. "Guitar pedalboards" are used by musicians who use multiple stomp-boxes; these may be a DIY project made with plywood or a commercial pedalboard made from metal.
Modern desktop and notebook computers often have sound processing capabilities that rival commercially available effects boxes. Some can process sound through VST or similar plugins, such as RTAS or Direct X. With a decent sound card, musicians can play any instrument through a computer, emulating effects units or amplifiers. Many VST-plugins are can be downloaded for little or no cost.
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