Hi,
Is it possible to use the AOE2 soundtrack for Youtube and/or Twitch? I’ve been searching for an answer by reading Microsoft their rules regarding author rights but I haven’t gotten a clear answer yet.
Hey. Sorry for the late answer 
Microsoft have a general info on their Xbox page:
If you want to use the soundtracks or audio effects from the original game, we often license those from or to third parties and don’t always have the rights to pass them on to you. If we do, we’ll let you know. For example, we might mention on the community website for a particular game whether you have these rights, so you’d do well to check. If we don’t let you know, you need permission from a third party, especially for games with licensed music.
Which unfortunately doesn’t answer the actual question.
It actually does:
We know that people like you – gamers, fans, individuals, and enthusiasts – love our games and sometimes want to use things like gameplay footage, screenshots, music, and other elements of our games (“Game Content”) to make things like machinima, videos, and other cool things (your “Item(s)”). We’d like to make that easier to do for fans of our games. So long as you can respect these rules, you can use our Game Content to make your Items.
Hmm I remember back around when DE launched I got some of my Twitch audio muted when using the official AOE2DE soundtrack. (Maybe because they offer it for sale?)
However I’ve used the original AOC soundtrack as well as the the AOE1DE soundtrack on Twitch without any issues. I’ve also used individual tracks by Vitalis Eirich, and those are fine too.
I’ve been using it in youtube videos for 2 years and have never received a strike. But I include always that reference in video description as per the linked rules state