Hi Country can help you implement this service to your customers.
It is illegal to place commercial music on hold on your phone system without an ASCAP license. Another option is to record the music yourself, find music that doesn't have an ASCAP restriction, or have a voice over completed. Here are some resources and options.
Music On Hold - definition and restrictions
Having music on hold problems ? Most of the problems we hear about are complaints from cell phone callers that the music on hold sounds terrible. Please realize that in the world of VoIP that some calls, especially mobile phones, use the G.729 compression algorithm and since G.729 is based upon phonetic human speech music will obviously not work well.