I can't add anything to what Ridge said in his excellent review, except to say that the music was in large part, responsible for evoking the feeling of the era. As the old commercial once said "Music is the soundtrack of our lives" or something like that. Of course the acting didn't hurt the movie either, but the music put the exclamation point on it.

This is a wall-to-wall sound track and is so good, that I slip the DVD in just to listen to it. The bar scene, where Sonny's crew demolishes the biker gang with Harvey & The Moonglows performing "Ten Commandments Of Love" is a classic. De Niro played this to the hilt. Between the lines, "Thou shall never love another" and "Stand by me all the while" is Sonny's voice yelling, "Kick his f--cking head in." Great stuff. Also on the sound track: "Come Together" (Beatles); "I Only Have Eyes for You" (The Flamingos); "A Beautiful Morning" (The Rascals); "I Wonder Why" (Dion DiMucci and The Belmonts); "Ain't That a Kick in the Head" (Dean Martin);"It's a Man's Man's Man's World" (James Brown & The Famous Flames); "Baby I Need Your Loving" (The Four Tops); "That's Life" (Frank Sinatra); "All Along the Watchtower" (Jimi Hendrix Expierience); "Don't You Just Know It" (Huey "Piano" Smith) & The Clowns); "Streets of the Bronx" (Cool Change); "Little Girl Of Mine" (The Cleftones); "Don't You Know" (Della Reese); "For Your Precious Love" (Jerry Butler & The Impressions); "Father And Son" (Cool Change); "Tell It Like It Is" (Aaron Neville); "Bustalk" (Bobby Watson); "Ninety-Nine And A Half" (Wilson Pickett); "Nights In White Satin" (The Moody Blues); "Regrets" (Butch Barbella); "I'm So Proud" (The Impressions); "Cristo Redentor" (Donald Byrd); "I Only Have Eyes For You" (The Complexions); "I Only Have Eyes For You" (Gerry Niewood); "Same Old Song and Dance" (Frank Sinatra); "Flamenco Sketches" (Miles Davis); "Ruby" (Adam Wade); "Sole Malato" (Domenico Modugno); "I Need Your Loving" (Don Gardner and Dee Dee Ford); "Ninety-Nine and a Half (Won't Do)" (Wilson Pickett); "When Joanna Loved Me" (Tony Bennett) and around 10 more, including "Strange Brew" by Cream. 

A great movie, for sure, and certainly good enough to buy just for the music...