for many years, I have been giving the example of "just intonation" as the Everly Brothers. such was their accuracy of intonation, I saw a documentary (which I have not seen for years) where they were performing in a clip, one of their famous tunes. the documentary then cut to them 30years later, and the song continued without any noticeable change.
their harmonies are unique in 'pop' music, and finally, I have encountered an example: here you have the brothers' harmonies (about 3mins 20 - and many examples later on) 'beating' with each other. not aware of any other examples. utter beauty.
(no, it's not the old recording, they did this many times)