How can I group songs in iTunes 12 from different albums into one collection?

Start by doing Control-click > Get Info on each song. Then scroll down on the "Details" tab to view "Album is part of a collection by various artists" as shown here. Check that box:

I think what you are wanting is for the tracks to group together as different albums but still retain their original album identity, right? This is a decidedly strange thing to want to do but you may be able to achieve it by giving the tracks a different sort album entry (see the "sorting" tab shown in an earlier post). Items with a common sort album short short by that entry but still display the original album.

mszebra wrote:

I tried your suggestion, but iTunes is still reading them as different albums.

because they are different albums.

would like to know how to organize a group of songs in such a way that each song can maintain their individual album titles (so that information is not lost), but they can be grouped together as one collection of songs that will play together--- basically, as one album among several albums within a playlist.

Put them all into the same playlist.