Youlean says that Freq-Balancer is a simple tool that will help you with mastering by balancing the frequency response of your songs. Here's Youlean's description in their own words...

What this plugin does:
Freq-Balancer analyzes the frequency content of an audio signal and automatically applies an equalizer that evens out the frequency balance towards a curve found on many commercial tracks. When Freq-Balancer analyses audio, it measures the audios frequency content over a period of time. It splits the incoming audio signal into 7 frequency bands. Then it measures and compares the audio levels within each band. Finally it applies EQ to compensate for any uneven frequency balance.

Typical applications:
The Freq-Balancer is mainly designed for mastering, but it can be used when mixing down songs, as well on the separate tracks. It can be used for analyze purposes only, or for both analyzes and correction. It can be helpful if you don't have high quality studio monitors, or if your room has no acoustic treatment, and the tracks you produce tend to have uneven frequency response.

Tips for mastering:
For best detection you must find the loudest and busiest part in the mix and then click "Learn". Try to avoid esses in vocals as it can make the result of analysis less accurate. To avoid it, you can loop part of the audio that doesn't contain esses. You will achieve best results if you insert this plugin after a compressor or limiter and then add the final master limiter after it, because too much dynamics could produce high spikes in some frequencies which will affect analysis. In most cases default settings will work well.   

Pricing and Availability:
Donationware

More information:

• Youlean