Remix in DanceXR means using motion data from one dance set and audio from another, and automatically adjust motion speed to match the music.
With this feature, you can adapt motions for different audio. And it will automatically adjust speed to match the motion and music.
How to Remix
Load a dance set with the audio you want to use. Then when you open the content menu to select dance sets, a  icon will appear next to them and you can use that button to load the dance set as a remix.
Once you have loaded a remix, you can see entries for both dance sets in your motion menu. There you can adjust settings for both dance sets.
When you use the content menu, it will automatically show  or  icons for new dance sets to allow you to quickly change the base dance set or the remix dance set. This is based on whether the dance set contains audio or not.
When you use remix, the motion speed is automatically adjusted to match the music. This is assuming that the timing settings for both base and remix dance sets are configured correctly.
In the remix settings, you can change a multiplier to further adjust speed.