I called a firm of solictors today and the phone rang once and then it was picked up by the voicemail queue which announced :-
"I'm afraid all the operators are busy at the moment but please hold and you will be transferred as soon as possible."
That was it, no confirmation that I'd called the right number by offering their name, no music on hold, no marketing messages. It's increasingly common to find firms using their "on hold" time to market the firm. There are a number of firms around the country who help with this, one in our neck of the woods is Sound Marketing.