Neither Rdio or Spotify are paying bounties to Twitter for new sign-ups, the companies confirmed.
Within a few hours of the service going live, new sign-ups and song plays on Rdio were already "spiking," said Malthe Sigurdsson, Rdio's vice president of product. "This is looking really good," he said.
As with many of the other tools that it has added since its inception seven years ago, Twitter bought the technology powering its music app from a startup. In this case, the music app is based on a concept and tools honed by We Are Hunted, which shut down its site for tracking popular music last week.
Twitter, which is based in San Francisco, is winning over advertisers, who typically must package their marketing messages in 140-character characters so that they fit seamlessly into the rest of the rapid-fire chatter flowing through users' feeds.
The company's worldwide ad revenue this year is expected to more than double to $583 million, up from $283 million last year. As a private company, Twitter doesn't disclose details about its financial performance.
That could change soon, though. There is mounting speculation that Twitter is expanding its services and selling ads more aggressively in preparation for an initial public offering of stock that could come late this year or early next year. If that were to happen, it would be the hottest technology IPO since Facebook went public nearly a year ago.
Twitter CEO Dick Costolo has repeatedly said that the company isn't under any pressure to go public because it has raised ample financing from investors, including a $400 million injection from venture capitalists in July 2011.
Business Writers Michael Liedtke in San Francisco and Barbara Ortutay in New York contributed to this report.