Soundproofing a room without deadening the sound


I'm turning a bedroom in my apartment into my listening room/office. The room backs up against my neighbor's room.

He's never complained about noise, but this will be a whole different level. Any suggestions for sound-proofing the room without deadening the sound or breaking the bank?
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Not practical, but I once had a buddy in a condo situation who put 2 inches of cork on an adjoining wall.
Acoustical treatment and sound proofing are like apples and oranges. Acoustical treating a room is rather a cheap affair if you are doing a home brew project. Sound proofing involves almost building another room within a room. The best of luck.