Tap-tuning — holding a plate loosely and tapping it to listen for a target pitch — is the oldest voicing method in the trade, and it still works, but it only gives you a single number: the plate’s dominant resonant frequency.
A Chladni pattern gives you something tap-tuning can’t: the actual shape of that vibration across the whole plate, not just its pitch. Two plates can tap to the identical pitch and show completely different nodal patterns, which usually means they’ll respond differently to a player’s actual bowing or picking, in ways a single tapped frequency will never reveal.
We still tap every plate first — it’s fast, and it’s a good sanity check — but the Chladni bench is where a plate’s final graduation actually gets decided.