There are companies that offer you a 'free' on hold demo, 'free' script writing, 'free' updates etc, the cost of which is recouped by getting you into a lengthy contract.
A typical Message on Hold program is 4 minutes long. Because a voice over talent typically reads between 100 and 112 words per minute, the script for a four-minute program can be up to 400 words, allowing for four to six paragraphs or messages, interspersed by brief intervals of music. Longer audio storage and program lengths are available if necessary.

The problem, in my mind, is that every single one of these articles misses the point completely. Even if you implemented a call centre system that detected and automatically played someone’s all-time favourite music while they waited, a facility which is possibly not that far off, most music when played down the phone just sounds terrible. Butchering a song that someone actually likes is unlikely to improve the waiting experience.
Please note that your phone system must have on-hold message capabilities to play an on-hold message. Click here if you need to find a phone system. A voice over script must accompany every order. The music is not available alone.