Time Out says
This state-of-the-art pop-up is the London home of the HighTide Festival
The influential HighTide festival has long been a bit of a mission for the average Londoner to get to, being based in Aldeburgh, Suffolk. But in 2017 it opens its debut London leg in Walthamstow. The Mix is a sophisticated pop-up venue that will set up in Walthamstow Town Square Gardens for a couple of weeks, and will presumably return in future years if the festival goes well.