"Free Music On Hold". No, I'm not talking about some kind of civil rights cause. I'm talking about your wise decision to put yourself in your customer's shoes and to try to enhance their calling and on-hold experiences. A couple of words of caution, however.
First, make sure you cover yourself legally by using only music that you are licensed to use.
Do some web searches for "music on hold copyright", etc. There are strict laws governing use of virtually any material - music or otherwise - which has been written, recorded, or produced by someone else. These laws are actively enforced, and substantial fines are levied against violators.
Second, if you don't have the budget for a professionally produced on-hold music and message production, "free" hold music is a good first step, but do your best to make it sound as professional as possible. Find the best quality music you can and play it on the highest quality player that you can afford. Take a hard look at your phone system. Is the sound quality of calls clear - both for callers on hold and when connected to an extension on the phone system (i.e., when talking to someone in your office)?
Call in to your business from several different outside telephone numbers and listen to the quality of the sound of the phones when someone answers the call as well as the quality of the on-hold sound. It shouldn't be noticeably scratchy or "tinny" sounding. It should be reasonably clear and you shouldn't have to strain to hear. Nothing about the experience should be distracting or annoying. If it is, go through the system piece by piece and identify and upgrade the offending elements. I.e., if there is bad sound quality the problem may be in the music player or in the phone system - or it could be in the phone line or the wiring between the "demarc" (point of demarcation) and your phone system. That is, it could be somewhere between the phone lines out "on the street" and your building or it could be somewhere in the building.
Make the calling and on-hold experience a pleasant one, and make it as easy as possible for your customers to be impressed with your professionalism. Just make sure you cover your legal bases in the process.