What legal rules do I have to go by when making an official collaboration album including different artists?

I will explain in more detail here. I work at a radio station and we get sent music through the mail from artists for us to play however we are going to make a official album using all different songs from the different artists CD's we have been given but what legal rules do I have to go by. For example do I need to have a license etc.
Answers:
Not knowing the details and not practicing in the area of copyright law, I am limited to giving you my general understanding of the matter. Your station needs to get an attorney involved to make sure that this is done correctly.
Generally speaking, artists have contracts with record companies that are "exclusive." In other words, for them to appear on an album put out by another company, they need permission from their company. That is why you will see the phrase "appears by permission of Dirty Dog Records" (or some other record company's name) on liner notes of duets.
Furthermore, once a song is recorded on an album, that record company has rights to that recording of the song. You will need a license or similar document from that record company giving you permission to use that track on a different CD. (In addition, there may be questions regarding payments to the songwriter and the studio musicians for using the song on a different CD.)
Copyright law is a very complex area. If your station does not have an attorney already, you need to find one who deals regularly in this area before you release any CD.

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you're asking here?
tell me you're kidding.
in venues such as this, the "average" IQ is 100, divided by the number of people.
surely you're not going to use this as justification for your actions. :-(

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The only thing I believe that should concern you is the area of copyright law. If you intend making an official album with a compilation of all the artists CD's you have been given ensure you have the permission to use the material. It is copyright and belongs to them. If you don't get permission then you can be sued.
Good luck!