Any tips for matching loudness on a batch of songs?

I've made 28 demo tracks for our band's repertoire, all nicely mixed and mastered in Ozone7. Each demo was a separate Sonar project.  In order to give them out on one CD I've tried hard to make them all sound similar in terms of loudness just using my ears, but I end up going back to successive projects to tweak their loudness via their Ozone7 controls and re-exporting. I'm in danger of getting into a  loop of continually 'shortening each table leg'.
Any quick and easy tips?  All I can think of is to import all 28 mastered WAVs into one Sonar project so that toggling between them is quicker and easier ears-wise, but then any that I change will need to be re-exported, is that ok quality wise?

Hopefully someone with Ozone 7 can chime in. I only did the trial, but the standalone version seemed like it had a layout to support album level matching. Not sure on that though.

If you have Adobe Audition, there is a feature called "match volume" which can be run as a batch routine. This will yield "RMS normalization" and has a few other options. Other wave editors may have similar, not sure, but Audition does for certain.

Ozone 7 may already have such in standalone mode (first option), but if this is a one-time thing, the trial of Adobe is fully functional (or used to be - check first).

I monitor the loudness of songs as I mix them using an European Broadcasting Union (EBU) meter. This has a thing that measures loudness over time. I tend to target -14 dB for most music, but sometimes go for -12.
 
When I measure LANDR masters, the lightest level of compression is usually around -13.2 dB loudness averaged over the song.
 
In any case, I imagine I'm bending something fragile to squish it into a box. I want to bend it as little as necessary to fit in the box I have for it.
 
To this end, I balance the various bending I do. I try to limit very little. The Concrete limiter shows how many dB it has limited at the max if you keep it open during playback. This is handy. Usually if it goes over 2 dB, I look to notch the spots with a volume envelope or perhaps add some lighter compression to the track that's causing the limiting.
 
So...
Playback and watch EBU meter. Set limiting sufficient to get to desired level on EBU meter (like -14).
 
If limiting is too much or becomes noticeable, increase compression only until you get the average loudness you seek with the limiting restrictions you set for yourself.
 
Now, one song, you may have to increase compression and limiting and another song you can back off compression and limiting. This may be counter-intuitive. In other words, Loud songs may need less compression and quiet ones may need more. It depends on the musicians playing the songs, but a loud distorted guitar often needs very little compression. The distortion IS the compression.
 
When a band has every song played loudly where the loudness is steady, that's when I consider mastering it to -13 or -12 dB. There are few peaks that need to be limited to get those extra few dB.
 
I've heard a lot of mixes mastered much louder than -12 dB, but I never do that. These are like the LANDR loud mixes. It just doesn't do it for me.
 
Now, when I finish with a show, all my tracks are roughly the same loudness. I might say this track needs a little more bass, or I want to hear more vocal there. Loudness, however, is constant.
 
It is true that one band mastered to -14 I can listen to at a nice high volume on my stereo where another also mastered to -14 will cause me to turn it down. Again, this might indicate that the first of the two could be upped to -12 dB.

Good meters. good ears, good dynamics/eq tools and a good plan it the only way to properly match songs.

That said, a Bluegrass number should not really be expected to match a Deathmetal track.

28 song demo?

Is this for a new member to learn songs or something?

If it really is a demo, I would pick your best 4 and match them up, much easier.

Some excellent suggestions here.  You could go with a lot of different stuff here but I think the simplest thing would be a Limiter like Boost11 or the Concrete Limiter.  Make the output the same for all of the songs i.e. -0.3.
 
rafone

Many thanks, some excellent suggestions!
I'm going to first try bringing them into Ozone7 standalone where they can all appear as separate tabs to toggle through. I'm not sure if all 28 will go in, but even four batches of seven will help greatly.  I have Studio One so their Project page is a good idea also.  Thanks everyone!
 
SimpleM - yes this is our 2x1 hour repetoire and we're bedding in a new lead singer. It also helps us all when practicing. I keep them on a hidden page on the band web site.  The curious can have a peep here:
http://www.thephoenixtrio.com/backing_tracks.html
 

1) Load each song in a separate project at the same time in Sonar
 
2) Find a convenient smallish size for the projects so that you can make a long cascade of all the songs from top left to bottom right. This makes it easier to flip between songs, see 5).
 
3) Add the mastering FX you think you will need to a song that is pretty representative and tweak until you are in the ballpark that you want all the songs to be. Write down which song it is!
 
4) Save as template and load that template into the rest of the songs
 
5) Tweak each song whilst flipping between your representative reference and other songs, starting and stopping playback as needed, until you are satisfied with all your songs.