Vol. 4: Harmonica Classics is a typically ace installment of the Blues Masters series has examples par excellence from most of the major electric blues harmonica geniuses, including Little Walter, Junior Wells, Sonny Boy Williamson, James Cotton, Paul Butterfield, Billy Boy Arnold, Lazy Lester, and Jimmy Reed. And while there are a few expected classics here (Little Walter's "Juke," Sonny Boy Williamson's "Help Me," Junior Wells' "Messin' with the Kid," Slim Harpo's "I Got Love if You Want It"), there are numerous delightful obscurities, like Jerry "Boogie" McCain's "Steady," Walter Horton's "Easy" (credited to Jimmy & Walter), and Snooky Pryor's "Boogie Twist." Charlie Musselwhite's 11-minute adaptation of the jazz tune "Christo Redemptor" is superb and challenges conventional ideas of what should and shouldn't be done with blues harmonica.