Orginate with ring tone for ConfBridge attendees

I am using Asterisk 16.2.1. I am able to utilize an IVR menu to bring in additional ConfBridge participants using Originate. While Originate is in progress I would like to have a ring tone on the bridge. After call is answered (or timeout) the ringing should stop.

This will start the ring while Originate is in progress:

[addcaller]
exten => 9,1,Originate(${john},exten,conferences,100,1,60,a)
exten => 9,2,Playtones(ring)

However, if I try to stop the ring like this it stops rings on the line of the person that answered the phone (and not stop it on the bridge):

[conferences]
exten => 100,1,StopPlayTones()
exten => 100,n,ConfBridge(1000,my_bridge,my_user,my_menu)

How do I stop the ringing for those on the bridge?

Thanks,

John