SurferEQ's real-time pitch detection engine is monophonic and therefore won't work well for polyphonic material in its regular Surf mode. However, SurferEQ can be fed with a MIDI track, pre-programmed with the fundamental chord movement of the song and use it as a pitch reference for the polyphonic content. Because harmonics are usually multiples of the fundamental frequency, SurferEQ can then be configured to adjust any harmonics of the polyphonic source.