As if answering some kind of Bat Signal -- perhaps there's a spotlight on top of the Hancock tower that throws a big purple Prince symbol into the sky -- pop megastar Prince swooped into to town this week, bringing the party -- and a few party fouls.

Near the end of his Monday night concert at United Center -- the first of three this week at the arena (plus three late-night shows at House of Blues, read on) in conjunction with the local Rebuild the Dream charity -- his crack NPG band started vamping into "Purple Rain." But Prince just had to explain his purple presence.

"Chicago, I don't want to preach," he lied, "but we need to love one another." He continued his homily, implicitly acknowledging the city's rough summer and his reason for being here, like some musical medicine man. "These are hard times, and they're gonna get harder. I don't need to be here; I want to be here." Earlier, as he was getting the party started, he instructed the sold-out crowd to "take your mind off all the problems outside."

Earlier this week, Madonna caused a minimal stir by sniping at Lady Gaga, referencing her during a concert and adding, "Imitation is the sincerest form of flattery."

Wednesday night at Chicago's United Center, the first of two concerts there this week, Madonna again slipped the chorus of Gaga's "Born This Way" into the bridge of her own "Express Yourself" -- it's a seamless match, for sure -- but let it go without comment. Well, almost. She shouted a bit from "She's Not Me" at the end.

Summer music festivals in Chicago are often maddeningly eclectic and increasingly
electronic. This year, though, some of the best moments at the biggies were when a rare
rock band hit the stage, such as at the Pitchfork Music Festival (Ty Segall, Wild Flag)
and Lollapalooza (Jack White, Black Sabbath, the Black Keys).

Now the transformation of Chicago's Riot Fest from a late-autumnal, five-day club haunt into a last-week-o'-
summer outdoor festival stabs a sharp period on the end of the season by blaring all rock and roll, all the time. Many shades of it, to be sure, but this new expansion brings welcome focus to a city that's been getting more attention for its EDM roots than its considerable rock and punk heritage.

The weather agreed. After an opening night (with Neon Trees, the Offspring and more) indoors at the Congress Theater, the eighth annual Riot Fest stepped outside for the first time on Saturday and Sunday into sunny, cool Humboldt Park, complete with four stages and carnival rides.

MTV's annual spectacle of, well, spectacle actually kept the lid on Thursday night and delivered two hours of stunt-free, solid live performances.

It's a weird cultural moment for the 31-year-old cable network and its annual Video Music Awards. The top three singles so far this year -- fun.'s "We Are Young," Carly Rae Jepsen's "Call Me Maybe," Gotye's "Somebody That I Used to Know" -- and all of the other nominees Thursday night became popular via numerous means, none of them MTV.

YouTube views, tweets, Facebook likes -- these are the street-level metrics determining what's momentarily hot and what's not nowadays. MTV has tried to fit in (the O Awards, anyone? Web 2.0 #fail) but largely has rested on the laurels of the VMAs' annual festival of carefully crafted outrageousness for attention.

This year, though, despite the usual advance hype about how totally cray the show would be, Friday morning's online a la carte video snippets will be short on shock value (other than the fact that dull boy band One Direction led the wins with three awards) but long on actual entertainment.

There are two ways of looking at Chicago's new West Loop restaurant and music venue, City Winery, just as there are two ways of looking at the fact that Fleetwood Mac's Lindsey Buckingham performed there this week.

City Winery is a swank, Sonoma-esque spot, all open air and exposed blond brick, with bottles and casks and tanks of wine in nearly every sight line. A series of connected spaces -- restaurant, bar, patio and the 300-seat listening room -- it buzzes with attentive staff and golf-shirted suburbanites. The tony décor and upscale menu (including dozens of superb wines on tap) intend to align themselves with similarly upscale artistry on stage, with upcoming singer-songwritery bookings building on the venue's original New York acclaim (below).

Which means it's easy to walk around the place and say, "Jeez, this place isn't very Chicago." And just as easy to exclaim, "Wow, it's like I'm not even in Chicago!"

Four years ago, electronic music pioneer Brian Eno released an acclaimed iPhone app, Bloom, which he called "part instrument, part composition and part artwork." The polyrhythmic space-jazz song "Bloom" -- which opens Radiohead's latest album, 2011's "The King of Limbs," and opened the band's concert Sunday night at the First Midwest Bank Amphitheatre in Tinley Park -- sounds basically like a fuller experience of the app.

Bloom, the app, is all about layering. A base tone hums, and you poke the screen to start certain notes looping, which causes a ripple effect on the display. Add some here, add some there, they repeat, repeat, and fade. Then you add some more. Eventually you realize that's all you can do with it and move along.

"Bloom," the song, started stacking its layers Sunday night before the band even hit the stage. Indistinct, spooky voices began looping. Radiohead drummer Phil Selway started playing. Portishead drummer Clive Deamer (touring with the band for extra oomph) started playing. Guitarist and keyboardist Jonny Greenwood started playing drums, too. With the groove laid and locked, ponytailed singer Thom Yorke stepped into the purple lights and began piling on his coos and wails. "Don't blow your mind with why," he sang.

Take his advice. Don't look too deeply into this experience anymore. After 20 years in business, Radiohead is a jam band now, a group of frustrated DJs making electronic dance music with live bass and drums. Songs, schmongs -- it's all about the layering, the groove. Why ask why?

In a venue already known for an angst-ridden wall, Roger Waters returned Friday night to Chicago to rebuild "The Wall" in the outfield of Wrigley Field.

Waters, 68, first brought his ever-ambitious construction/demolition tour to the United Center in September 2010. Friday night's "The Wall" was largely the same rock opera, brick by brick -- but with a wall twice as wide, stretching beyond both foul poles.

The ultimate symbol for many of this song cycle's timeless themes of alienation, disillusionment and mistrust of authority, the white foam-brick wall -- built up during the first act, then (spoiler alert) knocked down at the end of the second -- is three stories high, 140 yards across and ablaze throughout the concert with high-definition graphics and video from 42 synchronized projectors.

She was one girl among hundreds in line at a merchandise booth Saturday night inside Allstate Arena, waiting to buy One Direction mugs ($20), One Direction soda cups ($5), One Direction laminates ($10), One Direction glow sticks ($15), One Direction stickers ($5) and a dozen different One Direction T-shirts ($35-$40). Merchandise sales, in fact, opened on Friday to accommodate the throngs.

Hope, 12, was squeezing her mom's wallet and practically hyperventilating.

"I just can't believe it!" she gasped. "They're in this building right now! They're breathing the same air I am!"

If you haven't clued in to One Direction yet, be patient. A massive marketing machine is about to overheat in an effort to overexpose them.

When the Red Hot Chili Peppers returned to the stage Monday night at Allstate Arena, they did so one by one.

Drummer Chad Smith first leapt up and hung from a circular lighting rig before dropping onto the stool behind his enormous kit (complete with timpani). Guitarist Josh Klinghoffer emerged next, adding textured filigrees atop Smith's rebar rhythms. Bassist Flea walked in on his hands before picking up his bass for another thwackfest. The trio -- all eye contact and double-dog dares -- tore through their seventh sizzling jam of the night, and for a moment, well, you'd be forgiven if you hoped Anthony Kiedis wouldn't come back out.

Friday afternoon at Daley Center, folk-rocker Tom Morello roused the rally organized by National Nurses United by playing inspirational union songs. Then he tried to lead a sing-along of "This Land Is Your Land." But the crowd was young and, well, many didn't know the words.

That was not a problem Saturday night.

Closing out a sold-out show -- a concert called This Land Is Your Land: A Centennial Concert Celebration of the Legendary Woody Guthrie, at Metro in Wrigleyville -- Morello and the entire bill of more than 30 local musicians and international icons crowded the stage and sang every line to Guthrie's unofficial national anthem without any audience coaching. This crowd, though, was (at least in comparison with the usual rock mobs at Metro) not young. Many even knew the "censored" verses.

Saturday's tribute show crystallized in music much of what was being chanted, debated and discussed across Chicago during the weekend of the NATO summit and its corresponding protests.