Core Issue
Music on Hold, an application that may be installed to an media convergence server (MCS), streams Real-Time Protocol (RTP) audio in either unicast or multicast streams from the application server to the endpoint device.
Resolution
To disable Music on Hold (MOH), set the Run Flag to NO on all of the available MOH servers, so that MOH is not played from any of of the servers in the cluster. To do this, go to the Cisco CallManager Administration page > Service > Media Resource > Music on Hold Server.
For more information, refer to the How to disable Music on Hold for conference calls?section of CallManager Music on Hold Frequently Asked Questions.