In 2010, when the Justice Department allowed the two most dominant companies in the live music business — Live Nation and Ticketmaster — to merge, many greeted the news with dread.

Live Nation was already the world’s biggest concert promoter. Ticketmaster had for years been the leading ticket provider. Critics warned that the merger would create an industry monolith, one capable of crippling competitors in the ticketing business.

Federal officials tried to reassure the skeptics. They pointed to a consent decree, or legal settlement, they had negotiated as part of the merger approval. Its terms were strict, they said: It would boost competition and block monopolistic behavior by the new, larger Live Nation.

“There will be enough air and sunlight in this space for strong competitors to take root, grow and thrive,” said the country’s top antitrust regulator, Assistant Attorney General Christine A. Varney. And she went further, suggesting that reduced ticket service fees, even lower ticket prices, might be on the horizon.