LCD Soundsystem, one of the greatest bands to come out of New York in the ’00s, continue to function primarily as a live act. This fall, they’ll play residencies in Los Angeles and New York. But LCD Soundsystem don’t release new music very often. Two years ago, they dropped a track called “New Body Rhumba” on the soundtrack to Noah Baumbach’s White Noise movie. That one was the band’s first song in seven years. So it’s a big deal when a new LCD Soundsystem track pops up out of nowhere. One just did.