Independent record labels have said they are disappointed by the EU allowing Sony and BMG's merger, saying it was given "easy clearance".
Justin Timberlake is one of BMG's key artists
Lobby group Impala said the labels were "very disappointed" the EU's commission "authorized this merger".
It said it had been done "without any attempt to solve the competition issues that the commission itself identified."
The deal, approved without conditions, means the four major companies control around 80% of the world's music.
Impala said the labels "remain of the view that this decision is fundamentally flawed.
"This is a sad day for Europe's artists, entrepreneurs, culture, diversity and citizens," it said.
Impala president Michael Lambert said he had effectively been told a company with "50% share of the music market" was neither endangering European culture nor "thousands of young and small enterprises".
"This must be a b-movie. I will undoubtedly wake up tomorrow and realize just how bad and foolish my nightmare was," he said.
Sony said the decision to agree the merger was based on the state of the market.
"We're pleased that (EU officials) have recognized that the creation of Sony BMG is an appropriate and necessary response to current market conditions," said Sony Music Entertainment chairman and chief executive Andrew Lack on Monday.
But Martin Mills, another Impala board member and president of indie label Beggars Banquet, said: "In an over-regulated world, the regulators have sadly chosen not to support creativity in music.
"This merger is not about economic necessity in a changing market, as BMG's stellar figures demonstrate, it is about the desire to dominate and to control the outlets at media and retail level.