Apparently there is a feature in iTunes for "grouping" particular movements or pieces together - so if you have a CD with two symphonies, each containing several tracks, you can group the appropriate tracks together. I spotted one example of this in the iTunes store:
And when you click the arrows, the individual tracks of that "grouping" are hidden:
Is there any way to do this in a regular iTunes library, i.e. for the CDs that I've ripped myself?