HoRNet Autogain Pro MkII by Dysanfel
I once read that the use of automation to even out volume on a track is what separates good producers from great ones. If this is true HorNet has the tool that will make you great. AutoGain Pro Mk. II is the most inexpensive way to effectively write automation on instruments and vocals to even out volume. So, step away from the compressor!
There are other similar products. Waves makes VocalRider, but it is over $200. TBProAudio makes GainRider that is an alternative.
However, AutoGain Pro Mk.II is extremely easy to use and costs under $30. This is a no brainer.
No copy protection
Super competitive pricing
Rock solid coding even under heavy CPU loads