As you probably are aware of, there are more things than just games included with your Game Pass Ultimate subscription, as you also get EA Play, Xbox Cloud Gaming, discounts and something called perks. The latter is usually free DLC or virtual currency for games, and sometimes subscriptions on streaming services, but this time we're getting... relaxation.
Right now, Game Pass Ultimate subscribers gets a three month free trial of something called Calm Premium, which is "a wide range of content including a library of over 300 Sleep Stories to help you fall asleep, exclusive music tracks designed for focus and relaxation, and programs designed to guide you through meditation and movement".
As Xbox is offering this, there are even some game related soundscapes based on Halo Infinite and Sea of Thieves. The former lets you chillax to the ambient alien sounds of Zeta Halo, while the latter has soothing whirling waves from Rare's digital (and pirate infested) seas.
You must claim this perk before March 7, and if you like it, there is even a 50% discount after that. Head over to Xbox Wire to read more about this somewhat unconvential Xbox offering.