Tritone Digital has a FREE frequency-dependent phase rotation and correction plugin.
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PhaseTone allows you to manipulate the phase of your signal across a user-definable frequency range, with options for creating different phase and time-based offsets (if desired) for the left and right channels of a stereo signal.
Similar to hardware boxes popular for correcting phase relationships between signal-pairs such as bass DI and bass mics and top/bottom snare mics, PhaseTone goes a little further.
By allowing the user to select the center frequency and Q of the phase process, PhaseTone allows for more creative manipulation of phase when mixing, producing more EQ like results, increasing clarity and removing mud.
And, best of all, it’s free!