all understood but "at the time" this was a very common myth, that "Dolby cuts treble" it didn't. Of course, if the reverse expasion was switched off a treble lift was experienced along with the original noise but if people WANTED to listen to hacked up, noisy music that was their affair!
But then the duplicated musicassette was never going to be audiophile grade, even if the azimmuth matched the replay deck and the EQ was accurate AND the Dolby levels were spot on from the factory, it could not compare to vinyl, except of course for the absence of clicks! How many home recorders were setup for the tape types used? Often more than one type to boot..Effectively none and HF was the first casualty.
It is ironic that the digital technology that made CD cheaply available was also used for auto-bias/setup for tape, but sadly just too late. I had a Dolby HX Denon auto machine and with TDK AD it was superb.
And yes of course Hugh, all thing tend to droop with age.