How do I combine songs into one album on Apple Music?

Get into Songs view (select Songs in the sidebar). Select the tracks you want. Right-click and select 'Get Info'. For 'Album' you will see 'Mixed'.Delete that and give your new title. Click OK.

Doing the Playlist thing will allow you to keep the tracks' real album name.

I suggest that the easiest thing to do is to make a playlist of those tracks and then treat that playlist as though it was a single album:

How to create a playlist in the Apple Music app - Apple Support