Bitpunk on Nostr: I don't use BTCPay Server, but generally: With multisig, the private keys (seeds) ...

I don't use BTCPay Server, but generally:
With multisig, the private keys (seeds) from all the signers determine the public key. You ask if you can do that without changing the seed, no because now you have multiple seeds.

You can use the old singlesig seed as one of the signers, but it's better to rotate, and your addresses don't stay the same anyway.

It's hard to answer your question because you say different things, let me know if I can clarify a specific example 🙂