Hi, Ofcourse there's a description for the file format, it's just not released to the public. However, I managed to reverse engineer the most important parts of it to program an utility that simply loads wav files and creates exs instrument files for them. It also recreats the folder structure from which the wav:s were loaded, (that becomes the menus in the EXS24). I first tried this with a library of 2000 wav:s I have had om my HD for a long time that now are playable from the EXS24 :) I haven't reverse engineered all bytes of the exs file format, just enough to be able to create exs files (so far). If anyone's interested I'd be happy to share this little utility! I can also think of several features that could be added in the future. Note: The program only applies to PC and is only tested for the EXS24 that comes with Logic ver 5.5.1, it's also an early alfa release 0.0.1 Cheers everyone