Hi cbardens and greenberger,
jammr is designed for improvising together to a chord progression. It's not ideal for singing together because jammr is live but not real-time.
You hear what others played last time around the chord progression, and they hear what you played last time around. This works great for improvisation, taking turns soloing, practicing sections of a song, etc but not for things that really require real-time.
If you want to try creating a private jam session, you can do it as follows:
Click the “New jam” button in the “Connect to server…” dialog. You
will be in an empty jam session and can control who is allowed to join
by going to Admin | Access Control. Once you've entered your
bandmates' usernames they will see the jam session and be able to join
when they open the “Connect to server…” dialog.
See here for an overview of the user interface:
https://forum.jammr.net/topic/1727/Here is a guide to jamming successfully:
https://forum.jammr.net/topic/1724/