But while most such services operate under limited licenses that restrict what they can do with the music — for example, limiting the number of times songs by particular artist can be played within an hour — Apple is seeking direct licenses with record labels that would give the company more flexibility in using music, according to the people briefed on its plans.

Like Pandora, Apple’s radio service would have advertising, carried through Apple’s iAd platform. Whether Apple would then share part of the ad revenue with labels, or pay them some other licensing fee, was unclear. It was also unclear whether the service would be free or require a subscription. Pandora with ads is free, although its users can pay $36 a year for a service that eliminates the ads.

An Apple spokesman, as well as representatives of Sony Music, EMI and the Warner Music Group all declined to comment. A spokesman for the Universal Music Group could not be reached.

Apple’s plans were first reported by The Wall Street Journal on Thursday evening.

Apple’s service did not seem to be imminent; indeed, given the length of time it can take to negotiate licenses with the major labels, it could be months away. On Wednesday, Apple is expected to introduce its newest smartphone, the iPhone 5, but the people briefed on the company’s plans said it was unlikely that the custom radio feature would be part of that presentation.

Further complicating the process of licensing negotiations is the fact that much of the highest-level business of the music industry has ground to a near-halt this summer as the labels await decisions by government regulators in Europe and the United States about the Universal Music Group’s $1.9 billion takeover of EMI Music.