nokia audio manager (does this really work?)

i've had a 5510 before.. i wanted to have more mp3 on my phone that's why i tried to use the nokia audio manager to compress my mp3s.. later on i found out that it does'nt work.. same goes for the audio manager for 3300.. that's why i downloaded musicmatch and "another audio manager" for compressing/changing bit rates for mp3. could someone explain to me why the nokia audio manager does'nt work?