Monstercat Orchestral Suite is mash-up of various songs from Monstercat artists made by Stephen Walking. It was released on April 1, 2013 as an April Fools' joke, the song features no orchestra (you probably figured that one out).
The video was unfortunately delisted very quickly after being uploaded on the official Monstercat YouTube channel, but not completely removed.
On July 23, 2021, the video was suddenly made to private for reasons relating to a YouTube security update, which makes unlisted videos uploaded before January 1, 2017 to be made private.