Deep in West Philly, I'm staring up at the corner of a massive apartment building, looking for signs of an entrance.

A van pulls up and empties out. A gang of musicians hauls gear toward a garage door that opens in a series of reluctant metallic clicks. A steep grade leads to the summit, the place seemingly part of a former warehouse or parking garage.

A loft space opens up in the back, where, to the left, the bands will play, a mesh of punk and indie rock tucked away in a corner. The landing above is ignored; there will be no stage, no division between audience and performers. Everyone wants to get as close as possible, to sweat on, lean in, and, occasionally, sing with the bands playing tonight.

The D.I.Y. music scene in Philly is all about proximity. Audience members aren't just participants at shows; they actively support local bands, while helping to augment a circuit tying the Philly scene to similar scenes across much of North America.

That egalitarianism derives from, and is symbolized by, that absence of division. "Everyone's on the same tier," says Nick Morrison, singer for local band Mumblr.

"It's not like the TLA, where there's you and a performer," Mumblr drummer Scotty Stitzer says. "You're right there. You're helping create the experience."

Support means rapt attention amid frequent experimentation by bands that blend genres - as well as members. This is not a world dominated by booking agents. It's a world of repurposed kitchens and cramped basements where the water heater is not too far from the band.

"Vulnerability, not being afraid to put yourself out there, that's what the music, the scene is all about," says Kat Bean of Amanda X, a Philly female punk band.

While three-piece Philly punk trio the Chelsea Kills sonically tear up the space, I ask Morrison: How much of tonight's crowd is made up of musicians (on and off the bill)? "About a fourth," he says.

"As a musician," Bean says, "you're learning at every show." And every touring band, she adds, enriches the Philly sound.

So do the people out there who stay tied to the local scene via the Internet, such as friends in Baltimore who randomly call Mumblr, or the Penn State kids who found them on Facebook. Anyone can create these shows and promote the scene.

There's also a tradition of reciprocated hospitality: Houses usually put up and feed touring bands.

Websites such as Facebook and DODIY.org play huge roles. But word of mouth, everyone seems to agree, is paramount. As Nick Fanelli of Guild Shows, a group of five D.I.Y. promoters, says: "Once you have a house, they come." He tells of how Guild Shows once used three of their own houses as D.I.Y. spots. Finally finding a place to fit in upon moving to Philly, he says, was a "breath of fresh air."

"I got involved because all my friends were in bands," says Eric Osman, who started Lame-O Records in November 2012 while managing a band named Modern Baseball, made up of fellow Drexel students. He's currently on the road with them. "If I can find some music, and I can show people what they are missing, then let's do it."

Putting out records, such as the Hundred Acre Woods' first vinyl EP, Cold in the Morning, enables bands to make the leap from house basements to clubs, Osman says. His is one of a number of nascent D.I.Y. labels such as Ranch Records, Kat Kat Records, and Hot Green Records, the latter run by former members of the band Algernon Cadwallader.

As for that show in West Philly a few days before Christmas, it was hurriedly put together by promoter/guitarist Steve Kane, the show a hodgepodge of bands he has promoted on his Villanova radio program, The Kane Konundrum.

"After going to two shows," Kane says, "I asked the guys who lived there if I could put on a show, and they said, 'Send us a lineup.' "

In addition to bringing some friends' bands along, Kane's two-piece, Old Scratch, was on the bill.

"We all get into it for selfish reasons," Fanelli of Guild Shows says with a laugh. "First, it's about getting your band gigs. And then you want to help out the band you fall in love with the next week. It's infectious."

Ruben A. Polo, who runs booking for Kat Kat Records and plays in the band Secret Plot to Destroy the Entire Universe, started out with similar motivations. Mirroring the progression of bands in the scene, Polo and Fanelli have moved on to booking venues like Kung Fu Necktie and the Fire, in addition to D.I.Y. houses.

Along with Stitzer's uncle Josh Phillips (who runs a D.I.Y. house in Lansdowne), Fanelli and Polo represent more than a decade of playing music. Fanelli, like Kane, has been booking shows since he was 15.

A guy named Anthony, who doesn't want his last name in print, lives at a house booked by Fanelli and Polo, among others. "Once people play here," Anthony says, "they love it, and they can't wait to come back." Out-of-town bands return, and they frequently recommend the house, along with the promoters, to friends and friends of friends.

And then there are the videos, such as those capturing cult favorite Rasputin's Secret Police, for which Phillips drums. While cellphones remain in pockets, shows are frequently recorded. Greg Horbal, of Boston's Top Shelf Records and the Connecticut-based band the World Is a Beautiful Place & I Am No Longer Afraid to Die, says these D.I.Y. videos have people in the United Kingdom trying to emulate the scene: "They want that same energy."

"There's a rawness, an urgency to the music," says Ryan Monk of the Austin, Texas, D.I.Y. label Fleeting Youth Records. "And you get a sense of how tight-knit the scene is." While overall the Austin music scene is more famous, he calls its D.I.Y. scene "disjointed" compared with Philadelphia's. In addition to recent releases for Mumblr and the Chelsea Kills, Monk is looking to do a SXSW Philly showcase.

Amanda X will bring some of that Philly vibrancy to Montreal in May for Pouzza Fest. After a previous trip to that city, the band was recommended to the festival organizers by folks from Québécois D.I.Y. website Vakarme. That site, like Philadelphia's recent four-day, multivenue Kat Kat Fest, is a celebration of all things D.I.Y.

With old friends from previous tours and new friends looking to draw upon the Philadelphia energy, Bean says, "I can just look at the map and go."

Thus, the circuit is always rippling outward.