Look at the Mix Pyramid. Notice that the top or focal point of the pyramid is the lead vocal. The lead vocal or soloist must always be on top and be able to be understood by someone who does not already know the words to the song. Just under the lead vocals come the backing vocals or choir. They are the first layer of support, and they too need to be audible as a distinct musical element that helps convey the message of the song.
Beneath the vocals come the instruments that provide fill and color. These add musical interest and highlights, and in fact may be the most prominent portions of the mix when the vocalists are not singing. Instruments might include Lead Guitar, Synthesizer, Brass, and/or Percussion. These instruments will often lead between vocal lines or during instrumental breaks and may need a bit of help from the Mix Musician to make sure their parts are heard when needed.
The primary bed of chords that form the harmonies under the lead parts of the music are often laid down by instruments such as rhythm guitar, piano and/or electronic keyboards. These instruments should be audible but never dominant in the mix.
Lastly low frequency instruments add foundation and weight to the music. These include drums, bass guitar, organ pedals, and the low end of electronic keyboard instruments. While almost never dominant in the mix, if they are not given their proper place and balance in the mix, the music will sound thin and will lack much of its grandeur.
Your church buys its first in-ear system to replace the WL’s front/center wedge. The tech removes the wedge, and routes the WL’s monitor signal into the new IEM system. At sound check, the WL puts his earphones in and starts to sing and/or play. He promptly says “my mix is different!” The tech responds “nope, it’s the same mix you’ve always had”. Who’s right?
They both are. Remember that with the wedge, the WL heard the monitor signal AND his acoustic surroundings as a total package. Now that his ears are essentially plugged by earphones, he hears only the monitor signal provided, and DOES NOT hear his acoustic surroundings. He relies 100% on the monitor mix he receives. The tech is sending the same mix as before, in the wedge, but the monitoring experience now sounds totally and understandably different to the WL. For this reason, the transition can be startling and potentially frustrating for new IEM users.
A basic knowledge of music is important for the sound system operator unless only speech is amplified. When running a sound system you should consider yourself the “mix musician”. You will be balancing the musicians against each other and determining how the congregation hears them. As such you are an important part of the musical group, and need to understand what is important for music to sound good.
This does not mean you have to be able to play an instrument or read music (although that could not hurt). It does mean you need to understand some musical concepts and be able to speak the language of music in order to properly communicate with the other musicians in your role as the mix musician.