Earth Angel it is, Peter, and a good choice, because it is one of the "essential" doo-wop tunes--

Give it a good listen and pick out the following elements:

A)The unison sections(where the back up is not harmonized)

B)The places where "call and response" is used--

C)The places where the tenor's countermelody falls in

D)The places that the bass falls in

E)the way the back up changes on the bridge

F)The big ending

Pay particular attention to the way the vocal parts change as the song progresses--note the places that the lead singer is unaccompanied--Note all different ways chords are handled--depending on where they are used in the song--Also note the different endings for each section--

Amos is off base(nice guy though) in his analysis of Motown sessions--having worked a couple motown recording sessions, I can assure you that the folks there were very analytical about what they were doing--