Dr. Dre makes Apple debut at WWDC, helps showcase iPhone calling support in OS X Yosemite

Federighi made the call while on stage showcasing OS X Yosemite's new continuity features. In an effort to showcase how iPhone features can be wirelessly shared with the Mac — including the ability to place phone calls and talk over the Mac's microphone and speakers — Federighi said he would like to call one of Apple's newest employees.

On the Mac, he then placed a call to Dre, who answered with a stoic "hello" that appeared to surprise Federighi. Dre said that he's excited to begin life at Apple, before joking about what time he'd have to show up to work every day in order to beat notoriously early-rising Chief Executive Tim Cook.

Dre was brought onto Apple's team with its $3 billion purchase of streaming music provider and headphone maker Beats. Along with music industry mogul Jimmy Iovine, Dre turned beats into a premium brand that commands a huge chunk of the headphone market.

Apple has made it clear that the Beats acquisition is more about the streaming service than the headphone business, however. Cook noted in an interview that the Beats team gives Apple a "head start" in a business that is fast encroaching on iTunes's download sales domination.