Heritage Media Corp., New York, said it offered to buy the shares of POP Radio Corp. it doesn't already own in a stock swap. 

Heritage, which owns 51% of POP's 3.6 million shares outstanding, said it will exchange one share of a new preferred stock for each POP common share it doesn't already own.
Depending upon how many warrants and options are exercised prior to completion of the transaction, Heritage would issue between 1.8 million and 2.35 million preferred shares, a Heritage spokesman estimated.
In national over-the-counter trading yesterday, POP plunged $4 to $14.75. 

The preferred stock, which would have a dividend rate of $1.76 a year, would be convertible into Heritage common at a rate of four common shares for each preferred.
New York-based POP Radio provides, through a national, in-store network, a customized music, information and advertising service which simulates live radio.
Heritage owns and operates television and radio stations and in-store advertising and promotion programs.