What defines a high compliance cartridge vs low

Mechans, thanks so much for the detail; it is greatly appreciated.

There are very few high compliance cartridges left. Designers of moderately priced cartridges are using the Rega and VPI arms as design centers and at approximately 9 and 8 grams of effective mass these are medium mass arms.

I think that there is a focus on primary resonance simply because it is fairly easy to calculate, but the final sound is affected much more by arm/cartridge resonances that are higher in frequency than the primary resonance of the moving system. It's one more case of the wrong thing being easy to measure and the right thing being very hard to quantify.

I don't see putting a new cartridge on the Music Hall. It's like putting new tires on a car that you don't like. The 1042 is well regarded, so I don't think that is the issue. You may need to spend a bit more money to get there though. I would sell the Music Hall. You should be able to get a fair amount for it as they are popular. Again, just my opinion, but I would replace it with a Rega P3. It is a classic, and it has that wow factor.

As an aside, I am looking for a AE-3 to purchase. Would you be so kind as to share what mods you have done to it? Or is it the factory upgrades? Feel free to contact me directly if that is more convenient.