How to take off overdub effect from the existining recording

Guys, please help. I accidentaly recorded a mixtape with overdub feature on. As the result - the sound floats (volume of treble and high tones go up and down). Is it possible to somehow turned it off on the existing recording? Or any normalize/compression/etc. tricks that could cancel overdub effect (equilize the tones)?

Are you sure you did that, or did you produce the work with Windows Enhanced Services on? If you record in Overdub and only have one track, the tool doesn’t do anything. Enhanced Services is famous for affecting levels and tones.