A while back someone suggested CD Baby for downloadable MP3s. I search on the "contra dance" style, and add further parameters (say, "fiddle tune," or "instrumental"). When the tune lists appear, you can click on titles and listen to snippets.
Late last year I went looking for contra-styled versions of holiday carols, straight tempo and no singing; found enough to round out a December program.
It helps to have editing skills; I'm learning Audacity. Fun to make a tune a lot longer than presented on a recording, and when you have seven -- oh wait, make it six -- couples for a quadrille, longer pieces are good.
While I've sortof graduated to a laptop with SqView, the CD player and discs are always in my bag, and sometimes it's a lot easier to use that set-up. (The time I was set up on the sunny side of a pole barn, with the door open, and bright sunlight flooding the visual field...CDs.)
My PA is a Fender Passport, the one with six channels so I don't have to swap out gear when a few musicians show up, or the groom's father hands me a playlist device. It came with flimsy 25' cables, so I use my heavy 50' ones.
--Karen D.