Professional synthesizers like Korg, Roland ones have a extra 3-band-eq that fits its frequency dynamically to the note that played. So if I play a note and then one one octave higher, all frequencies of the eq bands will be doubled. In this way the character of the sound will not change no matter of the note, it seems to be part of the sound itself then.
Currently it seems to be very difficult to realize this by using the key tracker meta device + a filter device. It would be nice, if the key tracker would provide such algorithm, or another device.