To use Spotify Duo, one of the two people must be designated as the plan manager. This person sets up the payment method, sets the address, and invites the other member to join.

Google Duo is a free video chat app that lets you make video or voice calls and send messages from any device. Here's how to use it.

Duo Security adds a second layer of security to your online Calvin accounts.Duo is required for all students, staff, faculty members, and sponsored account holders.