Stand or sit in a circle.

One player, the Root, sings or plays a note.   Continue to play this Root note until it becomes a “drone.”

While the Root keeps droning on their note, everyone else starts to sing or play scales, phrases, or melodies using this root note as the root of a major scale.  You can do this by playing Tee Tee Notes on a Major scale from the Root note.  

When the Root feels everyone is comfortable with this tonal center, you say, “Root.”

Then the next player to the right of the Root becomes the Root. They pick a new root note. Everyone adapts their playing to this new root.

Continue around the circle, playing until everyone has a chance to be the Root several times. You need not limit yourselves to a major scale. Try having the scale be the blues scale or a mode or a scale you made up.

Also.  Instead of going around a circle in order, try letting anyone jump in as the next root, and no one has to actually say the word Root.

Also.  Try having each player pick a root note, and also one or two other notes to define a new scale/tonality.  Sing back and forth between these notes to help everyone else hear your scale/tonality.