It's the sounds of silence in Chicago.

After rock rasio station WLUP ("The Loop") bought up all 15,000 tickets to a Tom Petty and the Heartbreakers concert scheduled for Thursday, rival station WMET decided to boycott Petty's music, including his just-released MCA album "Hard Promises."

WLUP, formerly the highest-rated rock station in Chicago but now trailing WMET, offered to buy all the tickets to the Rosemont Horizon Rena show in order to give them away in station promotions according to Petty's manager Tony Dimitriades.

"Whilst I was considering the offer," Dimitriades said recently, "I got a call from their arch-rival, WMET, and to get it down to the basics, they threatened to stop playing Tom Petty's music. They said they have just received the new album, and they were excited about it, but they wouldn't be to excited if we did this promotion with The Loop.

"I spoke to Tom about it, and the most important motivating factor we couldn't get around was that 15,000 kids in Chicago were going to get in free . . . . If WMET had come to us with the idea, we would have done it with them."

WMET program director Tom Teuber confirmed that his station had ceased playing Tom Petty records, although they would "probably" return them to the playlist on June 12.