I’m also worried about how much of the harmonics in the music is LOST by the amp?


Of course, I don’t want gross harmonic distortion, but don’t abuse or lose the precious harmonics in the virgin recording either. No way to measure that, though, right? Thats where the ears come in…
redwoodaudio
EMI may well cause secondary and unwanted effects in amplifiers. One source is the speaker cables that are not only information bearers for analog audio signals. They are also RF antennas. The problem is that amplifiers may not have sufficient RF attenuation for RF related EMI fed into the amplifier via the speaker cables. As most amplifiers have an internal feedback signal from speaker output, RF noise can be injected into the negative feedback loop of the amplifier. This may well cause secondary effects for example within the micro-dynamics.
+1 atmasphere
Amplifier design guru Nelson Pass tinkers with harmonics sometimes adding more to his amp designs to get a pleasing sound. 
Numbers only get you so far - it’s the sound that sells. High end audio design is both science and art.
+1 atmasphere
Amplifier design guru Nelson Pass tinkers with harmonics sometimes adding more to his amp designs to get a pleasing sound.
If you are talking First Watt agree 100%. Pass Labs? Not so much. 
High end audio design is both science and art.
Yes. The trick is to design for the ear rather than the spec sheet. They are not the same :)

The spec sheet emphasizes low distortion, But it turns out that the ear will be less sensitive to distortion if the overall distortion has a certain signature: a predominate 2nd and/or 3rd harmonic in sufficient quantity to mask the higher orders. If this is the case then it will be very hard to tell the difference between 0.5%THD and 0.005THD.


If the lower orders are not in sufficient amplitudes, the higher orders (even if the amp has only 0.005% THD) will cause the amp to sound bright and harsh.


You have to know this simple fact when designing amps, if you want to make an amp that sounds like music rather than electronics.
@atmasphere if amps are not losing harmonic information wholesale, are the other components and cables generally more prone to losing it? Or is my worry about lost harmonics not necessary, and distortion the main culprit through the chain?