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The effective internal impedance (resistance which many change with signal frequency) of an electronic device. In modern audio equipment the output impedance is normally very low. Microphones are normally specified with an output impedance of 150 or 200 ohms, although some vintage designs might be as low as 30 Ohms.

Recording new material to separate tracks while auditioning and playing in synchronism with previously recorded material.

To exceed the maximum acceptable signal amplitude of an electronic or electrical circuit. Overloading a device results in a noticeable increase in distortion but this may be deemed musically beneficial and desirable, or completely unacceptable and inappropriate, depending on context and intent. Overloading an analogue device typically results in the waveform peaks becoming flattened (so tending towards a square wave) and a consequent rapid increase in odd-order harmonic distortion where the distortion products appear at higher frequencies than the source signal fundamentals, but remain musically related to them. In contrast, overloading a digital system inherently contravenes the Nyquest Theorum, since he generated harmonic distortion products generally extend far above half the sampling frequency, and so become aliased and actually appear at lower frequencies than the source fundamentals with a non-musical relationship. This is why digital overloads sound so obvous and unpleasant in comparison to analogue overloads.

A resistive circuit for reducing signal level.

A means of connecting two or more circuits together so that their inputs are connected together, and their outputs are all connected together.

The combination of fundamental and overtones together are called particals. (cf. harmonic)

A loudspeaker which requires an external power amplifier, the signal from which is passed to a passive cross-over filter. This splits and filters the signal to feed the two (or more) drive units.

A system of panel-mounted connectors used to bring inputs and outputs to a central point from where they can be routed using plug-in patch cords. Also called a Jackfield.

Peripheral Component Interconnect: an internal computer bus format used to integrating hardware devices such as sound cards. The PCI Local Bus has superseded earlier internal bus systems such as ISA and VESA, and although still very common on contemporary motherboards has, itself, now been superseded by faster interfaces such as PCI-X and PCI Express.