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Music Studio Technology
The Sound Mixer
The heart of a recording studio is a multi-channel mixer. Sound mixing has been incorporated into software associated with soundboards in computers and more people have access to them and can appreciate their intriguing properties. A home stereo amplifier has switches that select the sound source, but the sources cannot be mixed. You can listen to the Radio, Tape or CD but not all three at the same time. A mixer is more permissive because you can hear all the sound sources at once if you like, and adjust their position and relative importance in the mix.
Hardware mixing boards are found wherever music is performed or recorded. A mixing board in a recording or TV studio looks complicated but the concept is simple; a number of different signals enter the board, are processed by parallel channels and converge on a smaller number of outputs. A professional soundboard may have, for example, 16 input channels. The idea is that you mix up to 16 sound sources down to a two channel stereo output that is recorded on a tape or CD to be played on a stereo music system. If you are mixing the sound track of a new movie, you will have at least six output tracks to create the ”surround sound” effect. The incoming signals can be amplified and go through variety of processing steps.
The controls are knobs that rotate through 360 degrees and sliders that move up and down. The output of each channel is determined by a volume controller that changes volume smoothly from minimum to maximum – a typical analog control. All the sound sources can end up in the final mix and are positioned in an acoustic space by panning the sound to the left or right and adjusting the volume. The output mix involves adjusting hundreds of controllers; presetting most and moving others in real-time as the music is recorded. A recording engineer will have to listen to the mix repeatedly and practice real-time adjustments until the recording sounds right. The latest mixers are automated and remember slider and knob adjustments that have been made in the past.
To mix a singer and small band, for example, microphones pick up the sound and send millivolt signals into the mixer. Each instrument and vocalist gets a separate channel; a drum set may be recorded on several channels because a bass kick drum requires different sound processing than a snare drum or cymbal. A performance may be recorded at one session and parts are added at later sessions on separate channels. Many studio recordings are put together one track at a time and performers may never actually play together. A single vocalist may create a chorus by singing different parts at different times – each assigned to a different channel. When all the tracks are recorded, the engineer selects which tracks are included and adjusts the hundreds of variables controlling the mix until he or she achieves the finished song in stereo. The listener must be convinced that the song has been performed in real-time by a real ensemble.
Mixer in the Brain
The human brain, like the studio mixing board is a parallel processor with
many channels active at once. Consciousness is something like the output that
emerges from the monitor speakers when the signals from several tracks are
mixed. Activities on numerous tracks converge in consciousness. The brain allows
several tracks to be mixed, but one track is usually dominant and suppresses the
signals from other tracks. Humans have to focus on one task at a time and do not
tolerate distractions well. The idea of an executive function is an extension of
the mixer idea. Unlike the mixer in the recording studio, there is no recording
engineer so that the mixer in the brain is a self-regulating, recursive device.
The input signals themselves have to participate in regulating the selection of