I had an instance for the need of my laptop two weeks ago.
I was into the final set at a mostly seniors dance, when a crowd came in and started requesting fast party music. I had been playing a good mix, but they wanted line dancing like Electric Slide,YMCA,etc.
If I hadn't had party music on my laptop, there would have been a lot of angry people.
Bernie
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pa4X 76 ,SX900, Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station, Bose compact