NEW YORK (AP) ― Since its beginnings in the 1970s, rap music has transformed from an underground, street-based sound to a definitive part of pop culture, transcending race and becoming one of the strongest ― and most prolific ― voices of today’s generation. But at the Grammy Awards, rap has had a long-lasting losing streak in the top categories.

The hip-hop sound ― first recognized at the 1989 Grammys ― has seen numerous prestigious nominations over the years, and rap acts have either led or tied for most Grammy nominations for 10 of the last 14 years. But rarely will a hip-hop act win one of the show’s top four honors ― album, song and record of the year, along with best new artist.

Instead, rap acts tend to win rap awards.

50 Cent, who won his first and only Grammy two years ago, believes Grammy voters are out of touch and need a fresh outlook on contemporary music.

“I think that the board is a lot older and they’re conservative, so some of the content in the music is offensive on some level,’’ said 50 Cent, who famously interrupted Evanescence’s best new artist speech by walking onstage when he lost to the rock group in 2004. “There’s a lot of people that don’t accept that hip-hop culture is now pop culture.’’

This year, hip-hop leads the Grammys in nominations again, with Kanye West earning seven; it’s his third year as the show’s top-nominated act. While his song “All of the Lights’’ is up for song of the year, his critically revered fifth album, “My Beautiful Dark Twisted Fantasy,’’ didn’t score an album of the year nomination, a shock to many. Even Jimmy Jam ― the chair emeritus of the National Academy of Recording Arts and Sciences ― was surprised by West’s snub.

“I think he’s one of the genius artists, and I’m saying this as a person who’s worked with Michael Jackson and Prince, so I don’t throw that word around lightly,’’ Jam said. “So, yes, I was surprised.’’

West’s album with Jay-Z, “Watch the Throne,’’ was also left out of the top album category; both CDs are nominated for best rap album.

Jay-Z, who once boycotted the Grammys because of the show’s lack of love for hip-hop, says Grammy nominations are “cool,’’ but he doesn’t use the accolades as a barometer of his success.

“The Grammys and all of those other things, they’re fine and it’s a good way for everyone to get together amongst their peers and collect some trophies at the end of the night, but my whole thing is for the people, as long as the people accept it ― that’s my real Grammy,’’ Jay-Z said. “As long as it connects with an audience in a way.’’

But Steve Stoute, the former record executive who accused the Grammys of being irrelevant last year in a full-page advertisement in the New York Times after Eminem and Justin Bieber lost top awards, says there is a bigger problem. Stoute believes The Recording Academy doesn’t have board members who understand hip-hop as a true art form.

“If (The Recording Academy) understood that, then (rappers) would be scoring technical points,’’ he said. “They don’t get the technical points.’’

In Grammy history, 14 hip-hop albums have received nominations for album of the year. Lauryn Hill has the distinction of being the first hip-hop artist to win album of the year for “The Miseducation of Lauryn Hill’’ in 1999, but the album, while featuring rap, was heavy on R&B. Hill also won best new artist that year, the second time a rap-based act had done so following Arrested Development’s win in 1993. A rapper hasn’t won the award since.