Difference between Liability INsurance and Liability Waiver? (For Vendors)

So I found out that the string quartet that I booked doesn't have Liability insurance, but liability waivers? What is the difference?

I'm a littled annoyed, it is MY fault for not asking earlier, but i have a feeling the RH is not going to to for the waiver...I have to call today...if they don't I have to start from square one again looking for a string quartet!!!

If the vendor signs a waiver, it basically means that they will not sue the RH in the event of an accident. I doubt that the RH will accept a waiver in lieu of actual insurance, because there could be other situations that could happen. Imagine that the vendor starts a fire at the RH...why should the RH's insurance have to pay for it? If the vendor had insurance, the cost for repairs would be covered by the vendor's insurance.
If the vendor has actual insurance and an accident occurs, the insurance will cover any costs and the RH should not be liable.