Anyway he uses one system to listen to instrumental jazz, another for classical, and a third for vocals.I've heard this before.......and also the Hesson method of 'bright' and 'warm' cartridges balancing 'warm' and bright' LPs.
These don't seem to work that well for me as after I have decided that a 'full-bodied' cartridge like say the Fidelity Research FR-6SE is great for my 'bright' sounding LPs......when I switch to a more neutral cartridge directly after listening to this combination........I hear nuances that escaped the previous cartridge and re-listen to that 'bright' LP all over again.
I think that really good cartridges (and arms) are better than just 'tone-controls'.
They give one the ability to discover differences in presentation without changing speakers, amplification or rooms?
Then again there are folk who have different rooms, speakers and systems :-)