I got this response to a request I made in a drawthread at 4chan a while back. It's Beauty Brass fighting a Changeling during the Canterlot wedding invasion, using magical tuba powers to DOOT her foe into submission. It is a ponification of the "tuba gun" meme that came out of Japan several years ago, of course. I don't know who the artist is. It was posted anonymously. The style looks like it might be from Velgarn but I don't really know.