In cases where nothing else has been stated I'ld recommend speaking to the record company or the composer/artist. As for well known artists like Kanye West, Jay-Z, Mtley Cre etc. you'll most likely have to pay them money to get a license for their music.
There are websites where you can download music with free licenses that are free to use for non-commercial and in some cases commercial work aswell, can't recall exactly what their adresses were but I do think there's a thread here at unity-answers if I'm not mistaken, try searching.:)
There is even a HUGE page on this very site with free music portals. Just use search..
Hi Everyone,
I am new to Unity answers and I would want to greet everyone hello!
Well, if you are going to make a commercial game, I advice you to either ask the record company/composer/artist (like what Kona just mentioned above, go to websites with free-to-use music downloads or you could just compose your own music!
It doesn't hurt to make up your own awesome music! :)
This is my post from the collaboration section, hopefully it will be of help to you.
SoughtafterSounds.com provides professional music & sound design to independent game developers.
This includes film makers, advertising teams and organisations looking to include an originally composed audio architecture to their projects.
We provide originally composed pieces for commercial & non-commercial use.
Categories available: Sinister, Epic/Fight, Oriental - Chinese/Japanese, Chase Scene, Ambient, Sad/Emotional, Classical, Short Jingles & More.
You are free to use commercially licensed tracks for Adverts, Videos, Films, Video Games, Websites & more.
New Epic/Fight Category Available.
Introducing the Epic/Fight category as part of our library. There are at present 2 new and originally composed tracks with more due to be added very soon.
You are free to use these tracks in commercial applications with no fee's, upfront or otherwise to pay.
Just agree to license & notify via the notification form.
There is even a HUGE page on this very site with free music portals. Just use search..
– anon73820239