The offer, a good deal if even two people use it, is an attempt to bring down the cost of music for families that pay AT&T for cellphone service. It's part of Beats' major launch strategy since its headphone maker parent, Beats Electronics, bought streaming service MOG in 2012.
Beats Electronics is backed by hip-hop mogul Dr. Dre and former music executive Jimmy Iovine.
Beats Music works on the MOG platform, though the look and emphasis on human-curated playlists and recommendations are different.
With plans to add future promotional tie-ins with the popular headphone line, Beats Music would compete with services like Spotify, Rhapsody and Rdio. The family plan has a 90-day free trial but no free ad-supported version, unlike Spotify.
Beats Music CEO Ian Rogers said the company decided to launch its service with AT&T rather than do an immediate tie-in with a headphone purchase to reach the widest possible audience.
"We don't want people to think it's an ecosystem that's closed in some way," he said. Rogers gave a demo of the service this week on the sidelines of the International CES gadget show in Las Vegas.
David Christopher, chief marketing officer for Dallas-based AT&T Inc., said the company chose to partner with Beats Music because of a longstanding association with Iovine and the headphone line. It was also a way to get involved in transforming MOG.
"We were in on the ground floor with a shared vision about how we could really change the game for subscription music," Christopher said.