In the hours leading up to their showcase at The Chapel in San Francisco's Mission District in late February, members of HBK Gang milled about the overcrowded green room, laughing, dancing, and taking selfies. The effervescent supergroup consists of more than a dozen East Bay rappers, singers, and producers mostly in their early twenties. Many of them began making songs together in high school. They have a closeness that's palpable, and their effortless cross-promotion of one another's projects has turned their friendship into a movement. With Sage the Gemini, Iamsu!, Kool John, Kehlani, Jay Ant, Skipper, and P-Lo at the forefront of the group, HBK is part of a new generation of artists bringing national attention to the East Bay in the wake of the Aughts' influential yet nationally unsung hyphy movement.

Hyphy, a homegrown cultural phenomenon, created a local furor a decade ago, with artists such as Mac Dre, E-40, and Too $hort at its epicenter. But despite its regional popularity, it failed to garner a national audience and eventually lost momentum in the late 2000s, leaving the local rap scene in a lull.

Nonetheless, many artists argue that hyphy created a blueprint for the style of rap that now dominates the charts and nightclubs. And with the subgenre's noticeable influence on many out-of-town artists, some people in the local music industry are irked that it wasn't East Bay rappers who took the region's signature sound to the mainstream. Indeed, artists from bigger cities have become hugely successful through songs that use hyphy-influenced production and lyrical themes, while local artists have remained in their shadow — until recently.

HBK Day: Behind the Scenes from East Bay Express on Vimeo.

A polarizing figure in this debate is DJ Mustard, the most sought-after producer in hip-hop at the moment. A young Los Angeles native, Mustard has produced a number of hits during the past three years. 2 Chainz's "I'm Different," Jeremih's "Don't Tell 'Em," Big Sean's "I Don't Fuck With You," and Tyga's "Rack City" are just a few of the many tracks that kick off with the catchphrase, "Mustard on the beat, ho." With their thudding bass lines and sparse synth melodies, Mustard's beats bear great structural similarities to the hyphy songs that dominated local radio in the mid-2000s, and some people in the music industry have accused him of pilfering a distinctly Bay Area aesthetic.

"I definitely think the Bay Area doesn't get its credit for influencing the game," said Skipper when I pulled him aside at The Chapel while he waited to perform. In the background, Daghe, the group's DJ, played a mix of local and Top 40 hits, many Mustard-produced tracks among them. "Our sound is really poppin' off right now. Everything that's popular right now, all the songs you hear in the club, all the songs you hear on the radio — that sound, that bounce to it, is definitely Bay Area influenced."

While some major-label artists, such as Drake, are open about their admiration of Bay Area hip-hop, all too frequently, those who borrow from local rappers and producers' sound end up eclipsing them due to the lack of music industry infrastructure in this part of the state. Bay Area artists often don't have the resources to become stars in their own right, and, as a result, the appropriation of their music, slang, and culture has long gone unnoticed.

Things are changing, however, as the geographic lines that once barred success are dissolving thanks to YouTube and SoundCloud. HBK Gang's burgeoning artists have staked a claim to hip-hop on a national level, and their Bay Area peers — such as rappers G-Eazy and Bobby Brackins and producers NanosauR, Friendzone, and Nic Nac — have risen in tandem.

Many HBK members — who are only at the dawn of their careers — already boast viral videos and radio hits. They've received cosigns from Bay Area rap legends and mainstream artists alike.

With hit songs like "Gas Pedal" and "Only That Real," respectively, Sage the Gemini and Iamsu! accompanied platinum-selling rapper Wiz Khalifa on tour last summer and have worked with the likes of 2 Chainz. And Kehlani, Jay Ant, and Kool John recently got back from joining G-Eazy's "From the Bay to the Universe" tour, which included sold-out stops at iconic venues such as New York City's Webster Hall. P-Lo, HBK's most prolific beat maker, has produced hits for Yo Gotti and Tyga.

While DJ Mustard's hyphy-derived sound may have taken off before its pioneers got their due, members of HBK Gang are reclaiming their musical roots and using hyphy's legacy as a springboard for their own creative evolution.

The topic of appropriation is a sticky one, especially in hip-hop. In 2015, it's difficult to empirically calculate who has influenced whom, when so many rappers and producers rely heavily on samples, borrowed melodies, and guest verses. While some local artists have had a chip on their shoulder about the Bay Area's uncredited influence for years (to quote E-40 in his 2006 song "Tell Me When To Go," I'm from the Bay where we hyphy and go dumb/From the soil where them rappers be gettin' they lingo from), others have strategically overlooked it.

After all, collaborating with someone like DJ Mustard is more conducive to one's success than calling him out and inevitably looking petty. A conflict with a high-demand hitmaker could potentially compromise one's industry connections — a risk many up-and-coming artists don't want to take.