What is the maximum number of audio file uploads allowed?

What is the maximum number of audio files (uploaded mp3 files - not streams) that can be uploaded in a Bronze account? I am getting an error saying that I have reached the maximum amount of audio files for my account and that I must delete some in order to continue.
What is the maximum for Bronze? What is the maximum for Silver, Gold or Platinum?
Could I work around this by having two Bronze accounts?