Purity is defined as freedom from adulteration or contamination. In other words, nothing from the original is changed, added, or lost.
With respect to the audio reproduction chain, we know that to be impossible. Everything from the microphones to the loudspeakers to some degree adulterates and contaminates.
So the goal of a pure audio signal is a questionable value myth.
Try a glass of distilled water. Tasteless. Which is why most folks prefer fresh spring water or filtered tap water. It's the small impurities that give it flavor.
Recognizing the lack of purity is inevitable. Perhaps it's better to accept the idea that we're leaps and bounds ahead of the problem if we instead manage it to our advantage.
The asymptotic goal of achieving sonic purity can sometimes take away more than it adds.
