A musical ritual used to celebrate daily or extraordinary events in the community life of a math or concent. The music is performed a capella, using only the human voice and body-slapping. The community is called to the aut by a bell-ringing sequence.

The most prominant aut is Provener, which celebrates the daily winding of the great clock, just before the mid-day meal. It includes a lesson on past theoric accomplishments.

Other auts celebrate milestones in an avout's life, such as Eliger and Voco, or periodic events such as Apert.

The word Aut may be connected to the word act - substitution of act for aut works as well or better than subsitition of rite for aut throughout the book.

In an interview on the Bat Segundo Show #245, Neal Stephenson states the derivation of aut comes from the Spanish Inquisition's auto-da-fé or act of faith.