It's either the Main Street Electric Light Parade or SpectroMagic Parade. I think its the MSELP, but I'm getting older and the brain is a bit cobwebby.
We just saw them for the first time on Sunday, in this exact same spot. We talked to them and they introduced themselves as the Magic Kingdom Saxophone Quartet. We got the experience on video and I'm just getting ready to upload it to my YouTube page.