An audio mixer is an electronic device that channels incoming audio signals while maintaining control over such effects as volume level, tonality, placement, and other dynamics for music production. In professional sound mixing, this device is sometimes called a soundboard (sound board), mixing console, or mixer.
Traditional audio mixers are physical pieces of equipment with inputs for instruments and digital devices such as drum machines, auxiliary line-ins, and microphones. Mixing technology is also available via software, but requires an advanced sound card that features instrument inputs. Alternately, a person can transfer pre-recorded tracks to a computer for use with audio software.
Modern digital mixers are made for both professional and nonprofessional use, covering a wide range of quality and price. Studios commonly use a dedicated one, while in the nonprofessional market, it is often coupled with a digital recorder. The least expensive, nonprofessional models feature 4-track digital recording with built-in mixer. Additional channels add to the price, all else being equal, with high-end models featuring 24 channels.
Each channel on a mixer or soundboard is dedicated to a separate track, such as one channel for drums, one for lead guitar, rhythm, bass, keyboards, and so on. By keeping each instrument on its own track, channels not only stay clean of artifacts, but the sound engineer has maximum control over every element and aspect of the project.
Even after a track is recorded, the volume, echo, reverb, equalization, and various other effects can be applied as needed to tweak the sound. When tracks are played through the audio mixer simultaneously, the engineer can adjust or manipulate individual instruments or vocals to get the blend just right, as each channel has its own “lane” of controls. If drums overpower the mix at some point, they can be leveled down. If the lead guitar is buried, it can be brought out front. If vocals are muddy, they can be brightened.
A good audio mixer also features panoramic potentiometers otherwise known as “pan pots.” This control places an audio track to the left, center, or right within the mix to create a full stereo image. Traditionally, vocals are centered, with lead and rhythm guitars taking up opposite ends of the mix, and drums filling the background. This builds an acoustical environment, as if the band is surrounding the listener. Keyboards, percussion, and other instruments are also carefully placed within the image. In some instances, a drum roll or lead riff might “slide” or “roll” (pan) from one stereo channel to the other for effect, creating a sensation of movement.
In music production, the drum track is typically produced first, providing the foundation on which to build the other tracks. Once a second track is finished, it can be “bounced” to the drum track to free up another channel, and so on. Though there are limits to how many tracks can be bounced, even an inexpensive 4-track recorder with a built in mixer is generally capable of producing eight tracks or more. In all cases, the end result is mixed down to a 2-track stereo recording known as the “master,” from which a compact disk can be made for duplication.
Musicians who play at home and would like to record and produce their own original music may find that a mobile, palm-sized 4-channel audio mixer can be sufficient for the job. Some models come complete with built-in digital bass and drum kits for accompaniment, and an array of guitar effects. These affordable audio recorder/mixers won’t have the capability or control of larger, more professional models, but they do have astounding feature sets for their class. Some models use flash cards for unlimited memory, and many models offer universal serial bus (USB) or Firewire® ports so the final mix can be more easily transferred to a computer for burning to compact disk.
If the musician would like something with greater editing features, 8-16 track digital models might be a better choice. A mixer, recorder, and burner in one, the person can lay down his or her tracks, mix them, and burn the master to CD with a single machine that’s half the size of a laptop and a fraction of its weight. A similar but less expensive model will not include the burner, and the user can transfer the music to his or her computer to burn it.
A 24-track audio mixer is generally more soundboard than the average person needs, though standard in studio production. As expected, these models can cost a great deal of money, though a low-end model can be had for less. Before a musician purchases one, he or she would be wise to check for professional reviews along with consumer reviews.