J2B is an unique format, you can compare it with module files (extentions .mod .s3m .xm .it .psm etc etc). The OEM Beta versions of Jazz2 (1.00g and 1.00h are the only one we've ever seen) contain the original module files. These files are to download somewhere but I can't remember the URL... Somone will have to pop in to say it. You can save them as an MP3 using ModPlug Tracker which you can get here. Just open them up one by one, select File -> Save as MP3.