A music on hold adapter has an integrated analog adapter module which allows any and all of your phones to provide on hold audio content to ordinary analog and “KSU-Less” phone systems. Currently, when a caller is placed on hold with an ordinary phone, that call is routed back to your phone company. And there it sits.
Easy On Hold Founder Tim Brown says that the new scheduling mechanism is what makes the Easy On Hold streaming message unique. "The traditional four-minute on-hold loop, where several paragraphs are edited over one piece of music, is an outdated approach," he says. "Our service puts together a library of individual spots that can be told when to play and how often. You can schedule start and stop dates, too, so old content is never heard."

It's a place most of us have been before: Knowing that you have no option if you wish to get the help you need, you reply, “Sure, I’ll hold,” and politely wait. If you have never been through what comes next before, you are lucky. If I am being completely honest, I am slightly envious.
source: I have samsung galaxy y . i want to play music during call and callee can listen music. is there any app in android market? mikemangada Level 10 (Genius) Unfortunately there is no feature like this, If someone call you all media will be closed because how would you able to hear the person talking if the music is playing.