Some of the world's biggest music firms are the latest targets of New York attorney general Eliot Spitzer.
Getting onto a radio station play list can make or break a song
Mr Spitzer has served subpoenas on EMI, Universal Music, Sony BMG and Warner Music, the New York Times has reported.
The firms have been asked to hand over contracts, invoices and other documents as part of an inquiry into how songs make it on to radio station play lists.
EMI confirmed it was cooperating with the probe but stressed it had a policy banning unlawful promotion practices.
It added it had no reason to believe that there will be any material financial impact on the company.
Mr Spitzer's reputation is such that shares fell in London, Paris and New York.
EMI, whose artists include Coldplay and Kylie Minogue, closed down 1.36% in London on Friday.
Shares in Vivendi Universal, which owns Universal, closed 2.24% lower in Paris.
On Wall Street, Vivendi Universal closed down 3.03%; Time Warner, which owns Warner Music, lost 0.55%, and Sony slid 0.12%.
Mr Spitzer is currently going after some of the biggest names in the insurance industry, and has previously tangled with Wall Street and the mafia.
Sony BMG declined to comment on the report while Warner Music and Universal did not immediately return calls.
According to the New York Times, broadcasters are banned from taking cash or goods in return for playing songs.
The record industry, however, has long paid independent promoters as a way of skirting around this legislation, the paper alleges.
Independent promoters then pay radio stations an annual fee, not - they say - for playing a certain song, but for advance copies of play lists, the New York Times explained.
Mr Spitzer is said to allege that the agreement with the promoters severely hampers the chances of those artists who cannot afford to employ their services.