For instance, an mp3 can be losslessly compressed with 7zip to about 25% of its original size. I compressed an album and the whole thing is a 1/4 of the size. Each song is about a 1/4 of the size (a good double check)
As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance.If this question can be reworded to fit the rules in the help center, please edit the question.
The MP3 standard can encode sound to different quality levels, with different bitrates as a result. Your MP3 test sample must have been compressed to a very, very high bitrate initially. Try using a 128 kbps MP3, you'll see that it won't compress as much (if at all)