Have never seen Butch and magpie singing together but not uncommon I would think as a magpie is really a large butcherbird.

Wow! You found their nest! Cool! I like the clip with both of them singing. I managed to film a Butchie and Magpie singing together. Unfortunately by the time I got the camera the best part was over so it is pretty lousy footage but it is the only time we have seen this. We often hear a Magpie and a Butchie singing at the same time but have never seen them singing together. Just wondering if you came across something like that.