Are there any tools that apply an eq adjustment to the song itself?

Yes. Any high-level wave editor program will do. CoolEdit, SoundForge, etc.

Remember to apply your EQ settings to the raw ripped wave files before you compress them to MP3 format. You will lose quality if you decompress them from MP3, apply the EQ, then re-compress them to MP3.

Note that some wave editor programs will allow you to directly open and save to MP3 format. This is actually doing that same decompress/re-compress thing I described, it's just doing it "under the hood". You will still lose quality if you try to apply changes to an MP3 file. For best quality, you must work in the original wave format.

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Tony Fabris