With bc1p and MuSig2 key-path spending, multiple public keys are aggregated into a single public key, and the participants jointly produce one aggregate Schnorr signature. On-chain, observers can see only that single aggregate signature and cannot determine how many signers were involved or how many signatures were required to authorize the transaction. This provides the advantage of hiding the actual number of signers, but it is generally an n-of-n arrangement, meaning that every participant must take part in the signing process for the transaction to be completed. ₿🔐✍️