Geoffrey Ernest Emerick was an English sound engineer and record producer who worked with the Beatles on their albums Revolver (1966), Sgt. Pepper's Lonely Hearts Club Band (1967) and Abbey Road (1969). Beatles producer George Martin credited him with bringing "a new kind of mind to the recordings, always suggesting sonic ideas, different kinds of reverb, what we could do with the voices".

An audio engineer helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduction, and reinforcement of sound. Audio engineers work on the "technical aspect of recording—the placing of microphones, pre-amp knobs, the setting of levels. The physical recording of any project is done by an engineer…"