It’s been an interesting past two years on the charts for hip-hop. By this time last year, seven rap songs (including three from Drake) released in 2018 had reached No. 1 on the Billboard Hot 100. This year, only two 2019 rap songs (Lil Nas X’s “Old Town Road” and Post Malone and Swae Lee’s “Sunflower”) have managed to top the Hot 100.

To date, the year’s highest charting hip-hop songs include Lizzo’s “Truth Hurts” (No. 4), Post Malone’s “Goodbyes” (No. 3) featuring Young Thug and “Wow” (No. 2), Blueface’s “Thotiana” (No. 8), J. Cole’s Middle Child” (No. 4), DaBaby’s “Suge” (No. 7), Polo G and Lil Tjay’s “Pop Out” (No. 11), and Drake and Rick Ross’ “Money in the Grave” (No. 5). All of these songs move away from long-held conventions of what makes a rap hit.

“Suge” is a cartoonish party record peppered with warning shots. “Pop Out” is a street chronicle, complete with a catchy hook that doubles as the most menacing refrain in recent memory. “Thotiana” is essentially a Hot Boy manifesto. “Truth Hurts” and “Goodbyes” are both crossover pop-rap songs. “Wow” is a club record. “Middle Child” is part-braggadocio, part-stream of consciousness. And “Money in the Grave” is an all-purpose rap song courtesy of Drizzy and Rozay. There are no hooks from traditional R&B artists to be found.

In 2019, there is no longer a widely accepted, obvious pathway to a hit single. The standard formula we’ve all grown used to—the R&B-friendly rap song packaged to reach mass appeal—is nearly absent from the Hot 100 at the moment.

For roughly two decades, the fast track to a mainstream rap hit was to adopt a proven recipe that made the genre more digestible on a large scale: Take a familiar ’70s or ’80s funk, soul, or pop sample, flip it into a summer-ready soundscape, insert two to three verses, add an R&B hook (preferably by a recognizable singer), and you have a radio-friendly and commercially viable single.

The idea of inserting melody into hip-hop, whether performed by the rapper himself or with R&B assistance, is a concept that dates back decades. Rap’s earliest melodic excerpts were mostly comedic. Slick Rick embodied shower-singing on Doug E. Fresh’s “La Di Da Di” (1984) and Erick Sermon offered his best Luther Vandross impersonation on EPMD’s “So Wat Cha Sayin” (1989), while Biz Markie’s “Just a Friend” (1989), in which he interprets ’60s crooner Freddie Scott in his own inimitable way, is clearly parodic.

There were sprinkles of the formula being used throughout the ‘80s and early ‘90s, most notably in songs from LL Cool J, Heavy D & The Boyz, and Dr. Dre. But the concept was arguably perfected by Sean “Diddy” Combs: first through his work as an Uptown Records A&R with Jodeci and Mary J. Blige, and later at the helm of his own Bad Boy Records, overseeing the beatmaking collective the Hitmen.

The Notorious B.I.G.’s debut LP Ready to Die (1994) struck platinum, anchored by the success of singles “Juicy” featuring Total and “One More Chance (Stay Wit Me Remix)” featuring Faith Evans. The latter wasn’t included on the album, but helped promote it nonetheless. The music industry is a copycat business, so the formula became standard practice for major record labels seemingly overnight. 2pac, Nas, Lil’ Kim, and the Fugees, to name a few, all released formula-inspired hits on the heels of Bad Boy’s success. The idea later turned into a marketing tool and arguably reached peak popularity during the TRL and 106 & Park era in the aughts.

Often designated as something-for-the-ladies, or simply a girl song, the formula typically featured romantic or melodramatic plots and occasionally, party themes. There has been a slight adjustment to the concept, post-Drake, where rappers capable of hitting notes moonlight as crooners next to their R&B counterparts or shoulder the singing load themselves. While the production has evolved to match today’s sample-free, trap-centric climate, the central idea—combining rapping and melody while talking about romance or having a good time—hasn’t changed.

The decline of the formula coincides with the music industry transitioning from radio to streaming as a discovery tool.

Of 26 rap entries currently on the Hot 100—excluding songs from Drake’s Care Package re-release which initially arrived in earlier years—only Meek Mill’s “24/7” (No. 83) featuring Ella Mai and Big Sean’s “Single Again” (No. 84) featuring Jhene Aiko and Ty Dolla $ign use this approach. Two others—Young Thug’s “The London” with J. Cole and Travis Scott and Lil Nas X’s “Panini”—use a variation of the idea. “The London” is thematically disjointed and only references the formula in the soundbed and Travis’ hook, while “Panini” features alternative rock undertones in Take A Trip’s production and Nas X’s emo-inspired hook.

The decline of the formula coincides with the music industry transitioning from radio to streaming as a discovery tool. In the past three years (the window in which streaming services and their marquee playlists reached enough scale to become significant drivers of consumption), rap songs using the formula have been few and far between on the Hot 100.

According to Billboard’s Year-End Rap Songs Charts, there has been a significant drop in formula-driven songs from 2016 to 2018. The formula is becoming obsolete, in part because the idea is no longer effective, or easily identifiable.

Rap’s juggernauts are the exception to the new rule. Kendrick Lamar’s “Love” (No. 11) was one of the most streamed songs of 2017. Drake’s “In My Feelings,” a song that walks the line between hip-hop and R&B throughout, earned Drizzy his third No.1 of 2018. Cardi B had success with “Be Careful” (No. 11) and “Ring” featuring Kehlani (No. 28) last year, and more recently, “Please Me” with Bruno Mars (No. 3).

Meanwhile, J. Cole pivoted from the formula after 2013’s Born Sinner (the album included singles “Power Trip” featuring Miguel and “Crooked Smile” with TLC) and he hasn’t released a traditional single since. Born Sinner’s follow-up, 2014 Forest Hills Drive, is Cole’s best-selling album to date with upwards of three million album equivalent units in the U.S., and no formulaic single. Cole’s next two LPs have also gone platinum with a similar game plan. The aforementioned “Middle Child” was the first time Cole released a single leading up to a project in six years.

In contrast, some of Cole’s peers have stuck to their guns, but misfired. Wale has released a string of excellent singles with R&B assistance from Eric Bellinger (“Right Here”), Jacquees (“Black Bonnie”) and more recently, Jeremih (“On Chill”) in the last few years. But he’s yet to replicate the chart success of “Lotus Flower Bomb” with Miguel or “Bad” featuring Tiara Thomas. Kid Ink, who has almost exclusively lived off the formula for most of his career, has gone back to the drawing board on his last few singles. In fairness, “On Chill” is a fan favorite with early momentum. Time will tell if “Single Again” will go the distance and become another exception to the new rule.

The decline of the formula also seems to be transpiring during a loss in popularity for R&B and a blurring of genre lines that make hip-hop and R&B at times hardly distinguishable from one another. Today, songs with rappers as the primary artist are still difficult to define because of their rampant use of melody. The aforementioned “London” and “Panini” and say, 50 Cent’s “21 Questions,” share the same lineage, but they feel like distant relatives.

Whereas the idea of a radio song was pretty specific in the ‘90s and 2000s (so much so that KRS-One teamed up with R.E.M. to take some shots at the concept back in ‘91), the concept of a streaming-friendly song is much broader. Trap is the sound du jour, but the common threads and patterns between songs are difficult to pinpoint today—hence the range of subject matter from this year’s biggest rap songs.

The streaming model is to super-serve the audience, not force-feed it. Sure, playlists can operate as facilitators and at times, amplifiers, but streaming has democratized listening options. So the audience ultimately chooses their songs of choice, not the industry. And all signs point to listeners wanting more bangers, more blood, or perhaps, even more bars. Everything but the formula.