FLAC (Free Lossless Audio Codec) is a compressed lossless sound format popular on the Linux platform. It is possible to choose between different compression levels. Since the format is lossless, there is no downside in principle to choosing the highest possible compression, but it may make file saving operations significantly slower for a minor gain in file size.
When a multitrack document is saved as a FLAC file, Amadeus Pro will downmix it to a mono or stereo file, whichever is more suitable. Most text-based metadata is preserved in the FLAC file format, but artwork is lost.