February 24, 2005 was the end of an era. At least, that's how it looked to alt-rock fans across the Delaware Valley. For almost 12 years, they had been faithfully tuning their dials to 100.3 FM, also known as WPLY or Y100. Y100 was known in the area for devoting most of their airtime to alternative artists, and at their peak had attracted more than 500,000 listeners. However, on that unfortunate Thursday in February - after the last strains of Pearl Jam's "Alive" had faded out - Y100 officially went off the air.

The listeners protested immediately. 65,000 signed a petition to reinstate Y100 on the FM dial, but to no avail. Most of the station's former staff had moved on, but a few were determined to keep the station going. They created Y100rocks.com, a Web site where listeners could stream the same kind of programming they had heard on 100.3, running the operation out of former program director Jim McGuinn's spare bedroom.

"Our first thought was that someone would come and scoop it up and that we'd be back on the signal in no time," he says. "When that didn't happen, we just kept going." The next 17 months saw two more makeshift studios staffed by former listeners who volunteered their time to DJ. Their crude setup only worked in Y100's favor. They garnered attention for their D.I.Y.-style not only from music rags like Blender, Spin and Rolling Stone, but also from The New York Times, and provided more than 1.3 million streams to people across the United States as well as in 100 other countries. McGuinn describes this experience as eye-opening.

"Now with the Internet, the challenge flips over from people having too little choice on the AM/FM dial to people having a lot of choice," he says. "How do you stand out and attract an audience?" At the same time, the online format harmonized with Y100's core philosophy of connecting listeners with artists. "It was taking broadcasting back to the impulse of sharing culture within a community," he says.

Who can object to that? Certainly not WXPN, Penn's member-supported radio station. McGuinn had long been friends with Bruce Warren, XPN's assistant general manager of programming, and had guest-hosted shows there before. This connection and the similar ideologies of the two stations made it only natural that they should form a partnership. XPN believed it could reach a younger demographic through Y100, and Y100 was grateful for the chance to return to the airwaves and access XPN's facilities. And so, in August of 2006, Y100Rocks relocated to the XPN building and formally became Y-Rock on WXPN. Their programming maintains the same character that it has always had, though with bonuses. Their new status has given them the opportunity to do live concert broadcasts and "Radio Takeovers," wherein popular indie rock artists DJ a slot for the station. Participants have so far included Beck, The Shins, Modest Mouse, Spoon, Bloc Party, Lily Allen, and Travis. Sound good? You can hear Y-Rock on 88.5 FM on Wednesday and Thursday nights, 8-11 and Friday nights 7-11, and online every day at www.yrockonxpn.org.