This may be depending on the person, but I would recommend traditional Japanese and traditional Chinese music. Classical music and Jazz music are also good for this (to relax and/or relieve yourself from stress) in my opinion.
These genres are probably good for most of the people to relax and/or relieve themselves from stress, but some people are listening to other, different genres, for example rock, metal, hip-hop beats to relax and/or relieve themselves from stress.
Maybe other genres (for example ambient) or mixing the previously mentioned genres (for example mixing japanese classical music with hip-hop beats) are also good for you.
Reggae all day. It's uplifting, smooth, and life giving. It makes you feel like you're on an island. It's my fav music to relax to. You should check it out.
Artist like Steel Pulse, Richie Spice, & Stephen Marley are some of the guys I like.
For me it depends on what the person is stressed of. As for me, if I’m emotionally stress, I’ll listen to alternative rock songs from the bands Lifehouse, Far Away and etc. Also, since I’m a Christian, I listen to praise and worship songs either in victory or in defeat. Additionally, just to add, I also listen to classical music to make my mind more positive and motivated, classical music made my Wolfgang Amadeus Mozart, Hans Zimmer and even Ramin Dwajadi. The genre of the songs I’ve mentioned are effective to me and I apply it depending on the stress or struggle that I am facing. I hope it helps to other people that are dealing stress right now.