"Walk on the Wild Side" (Lou Reed)

Quite honestly, I didn't know what to make of "Walk on the Wild Side" from Transformer (1972) the first time I heard it as a pre-teen. At the time, I knew little or nothing about Lou Reed or the Velvets, so I had no clue the song was about actual people who were associated with Andy Warhol and his so-called Factory. I mean, even in context, it's still pretty peculiar: a jazz-inflected R&B song with half-spoken/half-sung vocals about transvestites and hustlers.
As Reed notes in this clip from the Classic Albums series, he'd been approached about turning Nelson Algren's gritty 1956 novel A Walk on the Wild Side into a musical.  So he composed a title song, only to have the writing team abandon the play for a different project. Reed had a song without a home, so he reworked it as a chronicle of the real-life characters he'd encountered at Warhol's Factory: Holly Woodlawn, Candy Darling, Joe Dallesandro, Joe "Sugar Plum Fairy" Campbell, and Jackie Curtis.
Despite knowing that those are/were real people, it didn't really sink in until I got the chance recently to visit Pittsburgh's Andy Warhol Museum, where there are numerous photographs (and occasionally videos) on display of those very folks. I got a pretty good sense of what life at Warhol's Union Square (NY) studio must have been like in the late 60s: a non-stop carnival of misfits looking for their place in the sun, shelter from the elements, or other misfits like themselves. And as much as they were parasites, trying to suck fame and sustenance from Warhol's very veins, they were his family, too. Strip away the campiness and glam of Warhol's photos of this brood, and there's an unmistakeable tenderness.
That's why, when I hear the strings swell behind Herbie Flowers's double-tracked bassline and the Thunderthighs singing their doo-do-doo-do-doo-do-do-doo's before that after-hours sax kicks in, I sense endearment behind the seediness now.
There's no judgment. No finger-wagging. It's just poetic honesty about some unconventional souls Reed once knew.

"Sweet Jane" (The Velvet Underground)

"Accessible" isn't a word that one uses when talking about The Velvet Underground.  Lou Reed & Co. never aimed for the mainstream.  Gutters, alleyways, and anywhere where the light was dim—that was more their territory.
However, after years of not selling any records, the band made an attempt at a pop album called Loaded (1970).  On it, is the track "Sweet Jane," perhaps Reed's most effervescent, accessible composition of all time.  Unlike a lot of songs in the band's catalog, you don't really have to get acclimated to "Sweet Jane" before it reveals its charms.  It hits you in the gut from moment one with its lean, mean riff, which lets you know it's destined for rock & roll immortality the moment you hear it.  (It's my personal favorite Reed riff, edging out "I'm Waiting for the Man" by a hair.)  
Nevertheless, Reed can't help himself from getting a little gritty, throwing in the suggestion that seemingly buttoned-up protagonists of the song, Jack and Jane, like to try on each other's clothes  (Jack's in his corset / Jane is in her vest).  To me, it was his way of pointing out that the mainstream is just as freaky as the fringe, even though outward appearances might lead you to believe otherwise.

"I'm Waiting for the Man" (The Velvet Underground)

Ah, Lou Reed.  If there's anything that you could count on, it was that he was predictably unpredictable.  (I mean, did anyone expect his disastrous collabo with Metallica, Lulu?)
Read anything about him, and you'll find that music journalists loathed interviewing him.  He was touchy, mercurial.  The only interview I've read that actually went well with Reed was a 1992 piece by writer Neil Gaiman.  
So why did people bother going back to the well, time after time, if the water was tainted?
All you have to do is listen to his storytelling on "I'm Waiting for the Man" from the groundbreaking, Andy Warhol-produced Velvet Underground & Nico (1967), and it becomes clear: he was the poet laureate of society's fringe.  Half participant, half reporter, he captures a gritty tableau of someone traveling from lower Manhattan to Harlem to buy $26 of heroin from his dealer (the "man"), who is consistently late.
For as immediate and rocking as the song is (it really is the blueprint for every punk garage band that followed), it's decidedly bleak, even though it's gracious in its reality.
Put it this way, if the song "Heroin" from the same album is the idealization of the drug, "I'm Waiting for the Man" is the harsh truth: it's a parasite that leaves you waiting in stairwells of rundown brownstones for a pricey hit of fleeting euphoria, inevitably followed by lingering hell.  (And they released that as a pop single.)
Thing is, Reed never judges or wags a finger.  He wasn't about that.  He was more about: here's the facts; make of them what you will.
And if you've wondered, like I have listening to Velvet Underground & Nico over the years, are half of the stories and characters that pop up in Reed's literate rock & roll true?  Here's what he told Gaiman in 1992:
"It's always kind of funny, over the years, people continuously asking me, 'Are these things based on reality?'  I thought it was so obvious that they were."

"Perfect Day" (Lou Reed)

Lou Reed—God rest his soul—was a curmudgeonly prick who was notoriously tight-lipped about the meaning of his songs.  But, damn, the man could write some memorable songs.
Over the years, I've read countless articles and people's web musings about the meaning of "Perfect Day."  One popular assertion is that it's a song about trying to kick heroin addiction.  But I don't really buy that theory.  Just because the film Trainspotting used it in the scene where Ewan McGregor's character, "Mark Renton," o.d.'s on heroin, doesn't make it a smack song.
The more plausible explanation is that Reed had fallen in love with cocktail waitress/aspiring actress Bettye Kronstadt—someone who was pretty far removed from the world of Andy Warhol's Factory and the various characters (transvestites, hustlers, junkies, socialites, and fame-seekers) that he had rubbed elbows with.  Thing was, he didn't really know what to make of Kronstadt, a nice, straight-laced girl who took him to sip sangria in Central Park, feed animals at the zoo, or go watch a movie like a "normal" couple.  He obviously found a certain comfort in going home to their love nest at the end of an evening rather than hitting the streets, looking to score drugs and/or sex.  Yet at the same time, he felt a bit disquieted at the prospect of domestic bliss; it's just not who he was.  
There's that heartbreaking stanza toward the end of the song, where he sings:
Just a perfect day
You made me forget myself
I thought I was someone else
Someone good 
Not to mention the very unromantic line he repeats at the very end: You're going to reap just what you sow.  Whether he's acknowledging to himself that the bliss is not going to last, or warning her that she's only going to get hurt, it is Reed at his cruelest (and that includes the sailor getting shot at the debauched party in "Sister Ray" and the partygoers being more worried about his blood staining the carpet than him dying from a bullet wound).
For me, the juxtaposition of sentimental strings against his self-analytical, very unsentimental musings make it less of a ballad about an idyllic day with a sweetheart and more of a commentary about the inevitable destructiveness of hypocrisy and self-deceit.  If there's anything Reed could do, it's tell the blunt, unvarnished truth.