Tone arm resonance and cartridge compliance: How do they interact??

I’ve seen low effective mass referred to as low moment of inertia. It is logical to conclude that a low moment of inertia arm requires and benefits from a low friction bearing.

Geoffrey Owen offers his Helius Omega Silver arm (used by Tim de Paravicini on his excellent EAR-Yoshino table) with the choice of Ruby or Silicon Nitride (Si 3N 4) ball bearings, both of which possess a hard, very smooth surface and therefore low friction, perfect for an arm’s bearings.

Plus, the effective mass of an arm varies depending on how far from the bearings is the counterweight. Some arms incorporate a counterweight that affords adjustable mass, the Zeta being one such.

In addition, while the arm and cartridge interaction does create a resonance, most (all?) armtubes have a resonant signature independent of that. Brooks Berdan used to (RIP) fill arm tubes with expandable foam to reduce armtube resonances, and the designer/maker of the excellent Audiomods arm installs braces inside his armtubes (just like the braces inside well-made loudspeaker enclosures) to raise the resonance in frequency.