MACE was an audio compression algorithm, usually seen used in non-lossless AIFF files. I know nothing about the technical aspects of MACE, but i used it a couple times around the mid-90s, and the quality was surprisingly good. It could get sound files down to what was, for the time, disturbingly small sizes-- the 6:1 level could get entire songs into 500k. The only problem is that it was very, very lossy, and the 6:1 sounded like it was playing over a telephone.. not good for music at all. These days, compared to MP3 and realaudio, MACE seems almost pathetic in terms of tradeoff between sound quality and file size, but for its time it was pretty cool.