Al, You, my friend, are a genius! The lack of sound in one channel was due to the fact that I temporarily hooked up one leg of the left channel without stripping the insulation. There was a good reason why I did this, which completely escapes me now. I forgot to go back and strip that leg before powering up the amp. There was no short, which is my worst nightmare in dealing with unterminated stranded wire. I quickly realized I had no sound from that channel and quickly (like 10 seconds) turned off the amp to avoid operating the dynamo without a load on one side. At that point, it was the end of the day, and I was tired, sweaty, and hot. I had no idea where my multimeter was, so I figured I needed to shut things down and try again with a fresh start. Good decision.
So your second scenario appears to be the correct one. It is nice to know there was a reasonable physical explanation for what I heard, other than that Rob and Bill don't know what music sounds like. It is kind of funny, because the sound was so bad it was exactly what I would expect old low tech speaker wire to sound like. Bad enough that 5 seconds of music was enough to tell me something was very wrong.