PlugIn Idea

I had an idea for a plugin last night that could have helped me alot in my mixing of two tunes, what if you had two tunes in different keys but the only note that stands out as being wrong in the mix was a bass note, what if there was a plugin that had a slider to change from low end to high end freq as a split point and you could then pitch either just the low end or the high end of the split point, just so you could tune that bass note that stands out from the mix, i would like to know if there is a plugin that would do this or something like this.
Advent57