As a facilitator I am focused on getting results, real, tangible, and measurable results. I also volunteer at a local hospital as a music therapist; there I am focused on comforting, healing, encouraging, and even entertaining. In both worlds I use music because it is a powerful tool.
We don't often think about music as a tool. We think about what music we like and don't like, when it is appropriate, whether it is too loud, but we seldom think about how to use it to accomplish a task.
In setting up a facilitated workshop, or any meeting, think about whether music will help you accomplish your desired outcome. Then decide whether and how to use it based on the value it will bring.
Sometimes I use music before a workshop begins to help set the mood (this is an example of abstract communication discussed on the consensus page). I also use it as a diversion to mark transitions. You might play something at the end of a break to bring people back together. Sometimes using cartoon theme songs for this can add a little levity to the workshop.
Background music can be helpful while people are doing group work. If you have multiple groups working in the same room the music can help mask other conversations. When using background music you need to choose music that won't interrupt discussions. For example, I love violin solos, but they are too distinctive for background music. I also love dramatic music with wide changes in volume, but these changes grab attention, making them a poor choice for background music. The volume is also critical. Watch people. If you notice their eyes dart toward the speakers when there is a change in the music then it is probably too loud.
You can also use music for significance. I sometimes use a fanfare, or solemn trumpet music (for example, Clarke's Trumpet Voluntary) as background for signing a plan, or to commemorate an important decision. I had one project manager that asked me to conclude a three day workshop with 'We Are the Champions' as he thanked people for their hard work.
In summary, music can be a very powerful tool, but it can also be disruptive and destroy the very thing you are trying to achieve. Plan it carefully and use it well.