Yes, everyone always refers to Russell O. Hamm paper but no one refers to any of these:
Mintz, R.S.: Comments on “Tubes Versus Transistors – Is there an Audible Difference?”, JAES (forum) Volume 21 p. 651; October 1973.
Trumbull, R.H.; More about 'Tubes versus Transistors', JAES (forum), Volume 22, p. 24, Jan/Feb 1974
Monteith, D.O.; Flowers, R.R.: Transistors Can Sound Better Than Tubes, JAES Volume 25 Issue 3 pp. 116-119; March 1977.
Which very convincingly dispell some conclusions of Hamm's paper. Particularly those about harmonic distortion characteristics inherent to devices. If Hamm's study would have had more samples of amplifiers, presenting various different designs one may commonly encounter, his results would have been much different and less straightforward.
Monteith and Flowers basically hit the nail on the head in their final conclusions:
In conclusion, the high voltage transistor preamplifier presented here supports the viewpoint of Mintz: 'In the field analysis, the characteristics of a typical system using transistors depends on the design, as is the case in tube circuits. A particular 'sound' may be incurred or avoided at the designer's pleasure no matter what active devices he uses.'
And in the light that the article presents a single-ended transistor mic pre amp, tuned for asymmetric clipping, which results to higher amount of even order harmonic distortion (unlike push-pull SS mic preamps tested by Hamm) the comment makes a lot of sense. Why did Hamm ignore that there are many different circuit architectures in both tube and SS categories? That was a paramount mistake.
Additionally, the thought process within may apply to HiFi design but when it comes to using distortion as -intentional- musical effect all "rules" fly out the window. Practice dispells his theory about what harmonics distorting tubes and solid-state amps produce, and not only that, practice also disagrees with Hamm's view about what harmonics are "musical". The theory about intervals of harmonic frequencies does seem sound at first, but unfortunately it just doesn't withstand any scrutiny with practical designs and applications that more or less use amps as sound effect processors. There are very few that actually work in a way outlined in Hamm's study.
Do note that these same "HiFi principles" also put ideal status to things like flat frequency response and high damping factor, while none of them is ideal for guitar amps either.
Upper odd harmonics may sound nasty when you listen them in a sine wave, but when you want to sound like Jimi Hendrix you simply can't do it without plenty of distortion, even, odd, high and low order. All those things can be good or bad, but it entirely depends on context and individual preferences. That's just how it goes, and Hamm's paper never even addresses this.
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