A live sound engineer controls the sound levels of all instruments and vocals during a concert. He or she adjusts the gain and volume levels as needed, and adds effects, to ensure that all instruments and vocals sound good together. He or she uses an audio mixing board to combine the input from all microphones on the stage. This is called front of house (FOH) mixer.
To get a good live mix, the engineer must have the technical knowledge to use the sound equipment. Basic knowledge of acoustics is also needed. Most importantly, the live sound engineer must be a creative person with a good ear for music.
The sound engineer’s job begins before the audience arrives for the show. Once all instruments, microphones, and other equipment are set up, the engineer completes a sound check. The band plays during a sound check and the engineer mixes the sound. Different mixes are created during the sound check.
The FOH mixer creates the sound that is sent to the loudspeakers for the audience to hear. Band members also need to hear themselves playing. Plus, each band member may want to hear a different mix. The drummer may want to hear more drums and bass in the mix, while the vocalist may want the vocals and guitar turned up.
These custom mixes are sent to the band members’ monitors. Monitors can be small speakers placed on the stage in front of each player, or earphones placed in a band member’s ear. The audience does not hear these monitor mixes. Monitor mixes can be sent from the FOH mixer, or from an auxiliary mixer.
The audio engineer can also add different effects during the mixing process. Effects such as compression, reverb, chorus, and other digital effects can be used to alter the sound. If effects were used during the original recording process, the live sound engineer may want to duplicate those effects. This will help the engineer achieve a live sound that is as close to the recording as possible.
An additional mixer may also be used if the live performance is being recorded. The live sound engineer may take on the role of recording engineer. He or she may also delegate this job to another engineer who specializes in recording.
When the show begins, the audience mix may need to be adjusted. When the sound check was completed, the concert hall was empty. When the concert hall is full of people, the acoustics of the room will change. The live sound engineer will adjust the sound mix as needed throughout the show.