Engine break in without a tachometer

I wonder if Joe Bonamassa just decides he's so good that he Tunes his guitar by ear and goes out there winging it every bite while the rest of the band uses an electric tuner.
I'll save y'all the wondering.. He doesn't

I think it's not really an issue with a stock type cam to just wing it , more than likely people end up low like 1900 rpm...anyway.