Using concise and simple words in your scripting helps ensure callers can comprehend what is being said. Although a complete on-hold message can be quite lengthy, it should include concise and to the point single messages. Aim to get each message across in around 35 to 40 words. Remember, what may read great in written word doesn't necessary sound great said out aloud.
source: May i know how to play music during a call and the song shoud be play to both at one time while on a call?is it is possible kindly suggest me sir.tha?

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Voice over Internet Protocol, similar to cellular networks, is handled digitally. Ringback is one way in which VoIP is setting itself apart from traditional telephony services. When you subscribe to business VoIP, your phone will most likely come pre-programmed with both ringback and on-hold music. VoIP providers, unlike cell phone carriers, don’t charge extra for ringback tones. Not only that, you can upload your own custom ringback and on-hold music, such as a favorite song, a customized soundtrack, or even a customized greeting or up-sell message. VoIP subscribers can select different connect and on-hold music by accessing their online portal.