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.
Most business-class phone systems come with a library of pre-recorded on-hold messages or music for you to choose from. They also typically allow you to upload your own, giving you the opportunity to customize your callers’ experience while they wait.

We put together some resources for a mix of both free-to-use and royalty-free hold music:
Have the ability to have music playing from the computer conected to the phone be the 'on hold' music a caller hears when put on hold. Search Search Searching… We have made changes to increase our security and have reset your password. We've just sent you an email to . Click the link to create a password, then come back here and sign in.