1.) Yes. If one song is quiet and another is loud, a normalizer will level out or "cushion" the changes in volume.
2.) Winamp plug-ins are add-ons that extend the features and functionality of Winamp. When you install a plug-in, a file (or files) is installed to the plug-ins directory. The plug-ins work/integrate with Winamp when Winamp is running. So, for short answer to the question – Yes.
Some normalizer plug-ins are DSP/Effect plug-ins. Configuration/options for DSP/Effect plug-ins can be can be found in Winamp by Ctrl+P (for preferences) > Plug-ins > DSP/Effect > select the plug-in from the plane/box in the right and click the 'Configure' button for options
Some normalizer plug-ins are Output plug-ins. Configuration/options for Output plug-ins can be can be found in Winamp by Ctrl+P (for preferences) > Plug-ins > Output > select the plug-in from the plane/box in the right and click the 'Configure' button for options
As a general "rule" for Output or DSP/Effect plug-ins the highlighted (or selected) plug-in is the current/active plug-in.
[Edit 01:06GMT > JonnyMac]
Something I forgot to mention, MP3Gain (from one of the threads) is a program separate from Winamp.
Originally posted by bodger99
that I did get from P2P.Thanks
The files with flat vocals may be sabotaged files put there by the RIAA & record companies.