Stereo Tool is a free Winamp plugin that can be used to manipulate sounds.
It was originally created to repair phase shift problems in stereo recordings, but it can do a lot more,
like keeping the Playback of each song at the same volume.
Currently, Stereo Tool offers the following sound processing options:
A singleband compressor/limiter
This can be used to make soft sounds louder or loud sounds softer, and to reduce loud peaks in the sound.
An 8-band multiband compressor/limiter
If one song contains a lot of bass, and the next contains a lot of treble, this filter can make them sound equal. Can also be used to keep the volume at the same level. At aggressive settings, the result sounds "fuller".
A stereo channel separation widener/narrower
With this you can move the instruments to the center, or further away from each other. This can be used among others to let both speakers play all the sounds at the same level (so if you only hear one speaker, you don't miss any sounds), and still keep a part of the stereo effect.
A stereo phase shift widener/narrower
Phase shift widening makes the stereo stand out more, which can make music sound more powerful. The instruments do not change position though. Phase shift narrowing can be useful for example if you have a mono output channel: Sounds converted to mono using this filter sound just as full and powerful as the original stereo recording. This enables transforming any recording to mono without audiable artifacts, and achieving better quality encoding for low BitRate MP3 files.
A phasing error (AZIMUTH) correction filter.
Old tape recordings and many cheap CDs often suffer from severe phasing errors. These phasing errors can make listening very unpleasant, and when the phasing error changes over time the sound can seem to "float" around you. It can also cause severe artifacts when converting the sound to mono or when playing it on a Surround system.
