"Peg" (Steely Dan)

By the time Steely Dan recorded its 1977 album Aja, the "band" consisted only of guitarist/bassist Walter Becker, vocalist/keyboardist Donald Fagen, and a revolving array of session players who were picked for what they could bring to an individual song.  Not a bad approach, actually.  If one player has blues chops, you plug him into a song that needs a bluesier feel.  Or if something calls for a jazzier approach, you use the guy who's a Wes Montgomery disciple for the guitar solo instead of the guy who was reared on Chuck Berry.  It was a smart way for Becker and Fagen to broaden Steely Dan's sonic palette and create music the way they heard it in their heads.
Anyway, the track "Peg" from Aja is what you get when Becker and Fagen create a "pop" song.  Its augmented blues structure makes it instantly accessible and familiar.  But then they throw in some quirky melodic twists (like the jazz-steeped chord changes on the chorus) and arranging innovations (like having Michael McDonald's backing vocal doubled by reed player Tom Scott on his Lyricon—an electronic sax-like instrument—to make the word "Peg!" sound strangely electronic and robotic) that catch you off guard and make you want to listen to it again, just so you can figure out what the hell is going on.
And then there's the lyrics.  In true Steely Dan fashion, they're smart but vague in their thrift.  The song is ostensibly about a young starlet who's about to get her big break in the movies.  However, Fagen drops subtle clues as to what kind of actress she might be; the fact that her headshot/pinup photo is blue suggests that her films might be equally blue.  (This no doubt eluded radio programmers, censors, and my 3-year-old brain when I first heard the song.)
But the song is really about the sum of its perfect parts.  It's the way Fagen's voice sounds against the galloping funk of Rick Marotta's drums and Chuck Rainey's bass; it's Jay Graydon's searing guitar solo, which defies any kind of categorization and comes completely out of left field.  Those elements are the reason why the song holds up to repeated plays instead of being stuck in the boneyard of late 70s R&B.