The instruments used, the parts they play and the structure of a song or piece of music. A skilful arranger can take any piece of music and totally change its feel or tone by adjusting these variables and the piece’s tonality.

echo – The physical reflection of a sound wave from a reflective surface which diminishes gradually in energy, thus getting quieter. Sound travels at roughly 340 meters per second (mps), so for a naturally occurring echo to be 1 second, the surface off which the original sound wave was reflected would have to be 170 metres away (170 m there and 170 m back).

gain – Amplification. Gain is determined by the amount an electronic circuit amplifies the input signal. The gain control on any device is therefore, very, very important. Setting a gain too low will mean the engineer has to compensate for low-level signals by increasing output volumes. This results in increased noise levels. Too much gain, and the signal will overload the input circuitry and result in distortion.

headphones – A small stereo loudspeaker system that can be worn on the head or in the ears to allow isolated monitoring of signals. May be referred to as ‘cans’.