I'm doing a quick test to see if people can tell the difference between various MP3 sampling rates (I know, it's been done a million times, but I want to see if musical training has any impact on the results). So, I imported the song into iTunes at 256 kbps. Then I put it into Garageband to edit the clip down to about 30 seconds in length. Then I exported to iTunes again, and used the "convert to MP3" function to make a 256 kbps, 128 kbps, and 64 kbps version. So, for all you audiophiles out there, is this a good way to create the sample files, or might something be lost in all those file conversions?