It is vital that you put your most important messages first, it’s all about interest and impact. It is a ‘Fact’ that 90% of callers put on hold without dialog or music will hang up within the first 40 seconds and 34% of those callers will be lost forever. Callers stay on hold up to three times longer with on hold messages.
If you need to use menu options for directing calls, try to keep these as short as possible, for example... “Thank you for calling Media Music Now. So that we can connect you to the most appropriate department, please choose from the following options: press 1 for general enquiries, press 2 for help with downloads and 3 for any other enquiries.

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.
If you still can’t find the right hold music or are lost among all the possibilities, you can create your own radio station that streams any music you’d like to your callers or upload your own MP3 files.