Complex sentence: There are two versions of the song, a stereo and mono version, with significant differences: the mono version (the original single) has the trademark psychedelic wah-wah guitar between lyric breaks, but the stereo version omits it.
Split into simpler sentences: There are two versions of the song, a stereo and mono version, each significantly different from the other. The mono version (the original single) has the trademark psychedelic wah-wah guitar between lyric breaks, but the stereo version omits it.