A recent Metafilter post introduces us to Galeazzo Frudua, a musician from Bologna, Italy who, "possesses an uncannily good ear for harmony, and has produced a series of videos that painstakingly and expertly analyze and demonstrate for you the vocal harmonies employed in various Beatles songs." These detailed tutorials, writes the Metafilter poster, are made all the more watchable by Frudua's "perceptive commentary, capable singing voice, unassuming manner, impressive video editing skills and, hey, his charming Italian accent."
In his first tutorial, for “Nowhere Man” (above), Frudua begins by introducing “Lennon voice”: “Lennon voice is very simple, and it goes like this.” And, handily, flawlessly, it does. Frudua, who seems to be recording in the back of a restaurant, matches the tone of Lennon, McCartney, and Harrison’s harmonies separately and together impressively. He particularly favors Rubber Soul. Hear his “In My Life” below. He calls it “one of the best performances ever of John Lennon in the Beatles” as well as “a fantastic campus on learning how to sing.”
Anecdotally, having worked with choir singers, opera singers, and a capella singers, I can say that Frudua’s ability is not particularly rare but is the effect of constant practice. One Metafilter poster puts it well: "It's not hard if you have a bit of an ear, and some experience.... Harmonies are a kind of language. Spend some time learning the grammar and a few phrases and it can open up quickly." Frudua’s not only a master of vocal harmony, he’s also an expert luthier and builds custom guitars for dozens of Italian artists. In his breakdown below of “You Never Give Me Your Money,” the intro to the Abbey Road medley, Frudua takes on a particularly difficult harmony, as he explains in great detail in his careful introduction to the song's harmonic grammar. He tells us we can use this tutorial “as a guide for your Beatles’ tribute band or reproduce them in your home recording.” You may do those things if you wish. Or you could watch Frudua do them better. See his full series here.