In reply to:
Tube amps are characterized by even ordered harmonics. Solid state amps by odd ordered harmonics. Music that sounds sonorous is characterized by even ordered harmonics. Noise is more akin to odd ordered harmonics. I wouldn't say that tube amps 'add' even ordered harmonics. It is the nature of the frequecy resonances, and I think even ordered harmonics are more musical than the odd ordered frequency resonances which characterize solid state amps.
YES... now we're getting somewhere. I won't argue semantics between distortion and harmonics - in this case, they're close enough that I'll accept them as nearly synonymous.
Now the difference between tube and S/S electronics is the level at which these harmonics (or distortion) are produced. For tube amplification, they're present at nearly every power level; for s/s amplification, the harmonics are introduced only when overdriven - if s/s distortion (read: harmonics if it makes you feel better) appeared at the same level as tube distortion (harmonics), a s/s amp would sound like FM radio tuned between channels.
In short - hopefully we can all agree on these points on both sides:
- odd order harmonics (ie: transistors) sound bad
- even order harmonics (ie: tubes) sound not so bad (really just "octaving" - at 12th intervals)
- tube amp reproduction demonstrates these "good" harmonics at all power levels
- S/S amp reproduction demonstrates these "bad" harmonics only when overdriven
- tube amps sound "round" because of the even order harmonics - the guitarded (players of 6-strings) among us will recognize the sound of an octaver
- s/s amps offer flat reproduction because of the (relative) lack of harmonic distortion until they are overdriven (at which point they exhibit ugly noisy distortion)
It's far oversimplified, but a good starting point for coming together.