It is not a synth on the recording. that"s May, all right. But the sound he gets has more to do with guitar than a effect pedal. i don"t know if you know that, but May built his own guitar from some silly kind of wood. and if you are listening to queen recordings, you will hear he has a lot of "hard to get effects". so don"t dwell on it, yust use a nice warm distortion and kick it!!