Q: There is a volume difference during playback on my iPod between different albums I have loaded. I have found and enabled the Sound Check setting under iTunes’ preferences but it hasn’t helped. I checked it after I loaded everything. Must I check the box first before I add the music files? Also, what is crossfade playback?
A: The Sound Check setting in iTunes itself does two things: First, it scans your music and other audio files to determine the necessary information to apply sound check to these tracks and adds the sound check volume adjustments, and secondly it actually enables the use of these adjustments when listening to music in iTunes itself.
To apply these settings on your iPod, however, you must enable the Sound Check setting separately on the iPod itself. This can be found under the “Settings” menu, and is simply a matter of being toggled on or off.
Sound Check does not need to be enabled in iTunes before importing tracks, since the first time you enable it, all existing tracks will be scanned to have the necessary volume adjustments applied. After this, any new tracks added to your library will have this information added to them as long as sound check is on when you’re importing them.
Once the volume adjustment information has been added to your files by iTunes, turning OFF the Sound Check option simply disables the feature for playback—any volume leveling information added to your tracks is retained. If you later re-enable Sound Check, it will therefore only need to scan those tracks that were added while you had it turned off. Further, other than to apply the sound check information itself, the setting in iTunes has no impact on the iPod setting.
Like the iPod, the Apple TV also has a sound check setting that can be accessed under the “Settings” menu. This works in the same fashion as it does on the iPod (ie, enables or disables the feature for tracks that already contain the necessary sound check information).
To answer your second question, the Crossfade Playback feature in iTunes is used for playing back non-gapless albums. Essentially, it fades down the volume at the end of the current track while simultaneously fading up the volume from the next track, creating a DJ-style overlap between two tracks while you’re listening to them. Note that this setting only applies when listening to tracks in iTunes (there is no equivalent setting on the iPod), and will not be used for any tracks that are marked as “Part of a Gapless Album” in the track info, as the cross-fade would get in the way of the normally-seamless transition between gapless tracks.