I'm sorry, telling, but it seems, your Discord embed might killed someone, literally.
For example, someone sent me a Discord message containing a Spotify embed and after me quietly clicking on the "Play" button, I jumped from the chair throwing away my headphones... Hears hurt. Shocking!
It appears, the volume of Discord was set to 10%, but Spotify played at freaking 100% without even allowing changing its volume. So, you ever play or not.
Hence, I don't even use Discord Spotify embeds, but just open these links in browser.
Check out YouTube embed which also uses user local storage for user settings(i.e. cookies).
All in all, please, consider appending a feature to control the volume of an embed.