I've always been fascinated by songs that use the flanging effect. I don't know why, technically I know exactly what this effect is, a comb filter, still it tickles a part of my auditory brain that says I can't get enough. In the old days there were two ways to obtain this effect, one was to create a delay by running tape through two tape recorders and adding together such that frequencies alternately cancelled and reinforced by slightly slowing one of them to get them not quite in sync, the other was to record mono on a stereo machine then skew the head slightly so the two tracks were out of phase while adding them together. Modern method is just to use a software comb filter but the effect is the same. You can also use a bucket-brigade reverb chip clocked at a high rate so the delay is very short but I haven't seen these used for decades.