Do not assume that the real tracks are mastered. Mastering is a process done to a group of songs, although we tend to apply the term to single songs.... the better term is "polish".... and no, the real tracks are recorded well but there is always room for improvement.

To get consistent levels, you need to start from the tracking stage.

As you move through your process, be sure the levels are good and strong but not clipping. On the export, shoot for a nice level with not a lot of massive compression. Just knock off the big spikes so the wave looks like this:



I have it in my audio editor WAVE PAD where I trim it and normalize it.

What you see there is the result of the export from Sonar before I normalize it. There is headroom there that normalizing will fill.

In Sonar I use Ozone to polish the mix and add some light compression to knock down and tame the bigger spikes.

Generally, at the end of this process, most of the songs are all at the same general level and nearly equal to radio ready levels.

Attaining a consistent level takes some time and practice but is not that hard to achieve.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.