Why Distortions Are So Bad!?

Regarding the recently introduced Trinity SRL Silver Reference mono power amplifiers and their extremely low distortions, Dietmar Bräuer provides some interesting insights. To better understand why distortions are sooooo bad, you need to understand what the spectrum of a note played by a musical instrument looks like. Attached are 3 spectra from 3 different instruments, all playing the same note A4. 

The fundamental note is always at 400 Hz. Whether it sounds like a saxophone or a flute depends only on the number and amplitude of the overtones produced by the instrument and the musician, which are at odd frequencies and even multiples of the fundamental.

In addition to the instrument itself, the skill of the musician also determines how this spectrum of overtones unfolds. This has been known for hundreds of years.
“Trumpets … sounding the 3rd and 5th … were more vibrant and … gave a wonderful echoic effect.” Samuel Pepys, 1633-1703
It is well known that even so-called high-end audio products produce harmonic distortions that are also odd and even multiples of the fundamental frequency.
In the playback chain, the harmonics naturally generated by the instrument are overlaid by these artificially generated distortions of the electronics.
In the sum, you hear the fundamental of the instrument together with the sum of the original overtone and the harmonic distortions of the electronics. 
In other words, the instrument’s harmonics/overtones are altered in amplitude and even in number.
The flute, for example, produces only even harmonics. If audio electronics also add odd harmonics, which almost all common electronic audio devices do, the result is a spectrum of tones that can never be produced by playing the flute.
If you change the amplitude and the number of original overtones of the instrument, the sound of this instrument will change audibly.
This leads to the often heard question: How do your electronics sound? 
Dietmar Bräuer: “As a designer of TRINITY electronic, I can say with absolute certainty that our high-end audio devices have no sound of their own.”