VoIP, or Voice Over IP, is becoming a very popular alternative to traditional phone lines. This type of service operates over the internet, allowing businesses to make calls without paying for a regular phone service. If you use VoIP, that is no reason to forego on hold messaging. In fact, many services are now VoIP compatible. This makes your low-cost phone option that much better, because you can still enjoy the same useful marketing service.
On Hold Messages from Impact help you stand out from competitors, make more sales, and keep clients happy.

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.
For those still using analogue or digital phone systems, voice on ISDN circuits has a bandwidth of around 4000Hz. The audio from an analogue phone is sampled at 8000Hz, and because of the nyquist theorem, must be low-pass filtered to 4000Hz. So any frequencies in the audio beyond 4000Hz are lost. Interestingly, the human ear and mind are good at recognising human speech, so this is considered "toll-quality" voice, i.e. good enough to pay for. This is the reason why certain vocalised letters are difficult or impossible to tell apart on the phone. For example, the differences between B, P, T, C, etc. are almost entirely above 4000Hz.