Limiting simultaneous arrangement elements to four prevents listener fatigue
A core rule from mixing practice: usually no more than four of the five arrangement elements (foundation, pad, rhythm, lead, fills) should play at the same time. Three elements often work well; all five simultaneously almost never works. When more than five elements occur together, the listener becomes confused and fatigued because the ear cannot decide where to focus. This is partly why great mixers make subtractive decisions — muting, pulling back, or re-timing elements — rather than just adding more. The rule applies regardless of how many total tracks are in the session; a session with 100 tracks still collapses to a manageable arrangement if only 3-4 elements play at any moment.
Examples
The bridge of a pop song where all parts drop out except lead vocal and kick drum effectively reduces to two elements — maximum impact. Contrast with a dense production where all five elements play through every section, producing fatigue.
Assessment
Given a session with drums, bass, pad synth, rhythm guitar, lead vocal, and two fill elements all playing simultaneously, name which element(s) you would mute or time to different sections, and explain why.