It's like creating a public key with multiple private keys, like multisig creates an single address by multiple pubkey, or Shamir creates a single seckey from multiple shares.

I am still studying this, but since it depends on schnorr signature, I think it will be difficult with the current nostr key (though proto NIP-95 exists already). it will have to start from a new key, won't it? 

 can't you do something like musig with schnorr quite easily? 

 About what?  What I mention is whether we can seamlessly verify the signatures attached to the nevent signed with the current private key vs. the new set of keys based on FROST, even if it is the same pubkey. I'm not sure.