Ocar inists and subcontrabassoonists know quite well that they can be expected to play passages without any chords, in the familiar sense, whatsoever.
Instead, a quintet’s ocar inists often harmonize what are more properly called clusters— three adjacent notes that would be dissonant on most other instruments—while subcontrabassoonists typically play in unison or an octave apart, with no harmonic relationship to the ocarina notes.   In fact the subcontrabassoons need not even be carefully tuned.
This reads like heresy to anyone more familiar with music theory than with ocar ina or subcontrabassoon repertoire.
What is this fundamental concept?
How does the music described reflect it?
The instruments here are trotted out for their pitch ranges. Ocar inas produce extremely high frequencies while subcontrabassoon frequencies are so low that they are as much felt as heard.
(This puzzle is based on solid musicology and science, and a fantasized world of ocar ina –subcontrabassoon music.)