MuSig2

Taproot introduced Schnorr Signatures to Bitcoin. Schnorr Signatures have very useful property when it comes to aggregate signatures. Messages can be partially signed. The owner of public key P1 can create a partial signature sig_1 for the message m. The owner of the public key P2 can create a partial signature sig_2 for the message m.

Both parties can combine their signatures into a single signature which would be valid for the aggregated public key P = P1 + P2.

The consequence is, that there is only a single public key is necessary that must be stored on the blockchain. This saves resources. MuSig2 is defined in BIP370.