IMS is an application that lets you create your own solution for on-hold customers. It comes pre-loaded with a few voice messages and a few melodies that you can serve to your customers while they wait on the line. This is a nice application to have if your telephone system goes into your Mac and you don't want to pay for an expensive third-party system to be installed in your office.
You can of course add your own messages and music files to customize the service. This task is very easy. You simply need to go to File, Load, and select an MP3 or WAV file. Then it will be listed in the main window and you can play it, rename it or change a few settings for that particular file. For example, if you add a voice message and a song, you can choose whether or not the message should be mixed with your music. You can assign a rotation rate to each message. This determines how often the message will be mixed with music. You can also choose what days you want the message to be active.
In my testing, I wasn't able to do much with IMS. It asked me to install a daemon utility, for which it needed root access. So I agreed by typing my password. After that, it asked me my password again to run the daemon service, and I agreed as well, but the pop-up window kept on appearing, which effectively turned the application useless for me. I must have entered my password 3 or 4 times before I gave up.