Now it's common practice for hip-hop and R&B to intertwine, but the '90s marked an era where the lines didn't quite yet blur. Rappers were rappers, singers were singers. Sometimes one would parlay into the other, but for the most part, if an R&B chanteuse wanted a rapper on a song, she would get one rather than try to rap herself.

As an homage to days past, The BoomBox has compiled standout collaborations from that famed era in music. While some choices weren't radio fixtures -- we just loved them -- others became soundtracks to life events. Check out the list and find out if any bring back some memories.

15. "Ain't Nobody," Monica Featuring Treach

The 'Nutty Professor' soundtrack was one of hip-hop and R&B's most classic collection of songs. Jay-Z and Foxy Brown's pairing for 'Ain't No N----' appeared on this soundtrack, along with other tracks like AZ Yet's erotic 'Last Night.' Another collaborative gem on the project came from Monica and Treach of Naughty By Nature. The R&B siren was always so good at crafting these romantic yet simple street symphonies of Juliet meets Romeo. This track was no exception, and hearing Treach on a love song was a pleasant surprise.

14. "It's a Party," Zhane Featuring Busta Rhymes

 Zhane hit big with the 1994 smash song, 'Hey Mr. DJ.' However, one of the follow-up singles, 'It's a Party,' embodied the house party vibe of the '90s. With Busta Rhymes assisting, the track has this mellowed soulful backdrop as he rhymes about parking-lot pimping, weed and hustling -- essential elements of any house party, right? Zhane took the lyrics in a different route, focusing on dancing and just having a good time -- the best of both worlds.

13. "Can't Be Wasting My Time," Mona Lisa Featuring Mister Cheeks

Another film score gem, Mona Lisa's single was found on the 'Don't Be a Menace' soundtrack. Lost Boyz' Mister Cheeks was already a seasoned veteran in the game of love at this time. After all, he lost his shorty named 'Renee' just a few songs prior. On this one, Cheeks says, "Yo Mona Lisa, see there's something that we both should understand. Now if we share life, you be my wife and I'll be your man." Was he proposing to her? Sounds like it!

12. "Just Like Me," Usher Featuring Lil Kim

Long before Nicki Minaj was a 'Lil Freak' in Usher's video, another blonde bombshell was riding shotgun on Usher's track. Lil' Kim appeared on Ursh's breakout album, 'My Way,' grunting like a feminine Rick Ross in 'Just Like Me.' The Queen Bee shares sentiments of being the baddest and only getting paid to play. Usher chimes in, chipping away at Kim's rough exterior, getting her to admit she's lonely sometimes too. Aren't we all?

11. "Sumthin' Wicked This Way Comes," TLC Featuring Andre 3000

Anyone who played TLC's classic LP 'CrazySexyCool' knows this closing song. "Remember back in the time when the only sign we had was pickets? But now in '94 it be this way something come wicked," Andre muses at the beginning of the song. His bars take out a chunk of the track, but they're so potent -- packed with anti-gang fodder and a slight jab at the late Michael Jackson. T-Boz and Chilli continue that progression of self-actualization, as Left Eye closes with an introspective-yet-cryptic verse about finding peace.

10. "So Good (Remix)," Davina Featuring Raekwon

Here's another example where a tough-edged rapper softens up to woo his lady -- calling her an "ice cream" flavor didn't quite drive that point home. Davina gets all philosophical with lines like, "And the joy that your lovin' brings, can separate the mountains from the sea." Raekwon the Chef balances it out by cooking up some bars about street love. It's the perfect combination of bad-boy-with-a-heart meets daydreaming-girl-with-a-book-of-poetry.

9. "Touch Me, Tease Me," Case Featuring Foxy Brown & Mary J. Blige

Mary J. Blige singing background on a song? That may seem hard to comprehend considering she's known for being the Queen of Hip-Hop Soul, but back in 1996, Mary took a backseat on 'Touch Me, Tease Me' and the stars of the show were Case and Foxy Brown. Another single off the 'Nutty Professor' soundtrack, this one shows Foxy telling Case to keep her "laced up" in the finest threads and she'll play her position as the Bonnie to his Clyde. Meanwhile, Case was professing his love for the Fox Boogie. Classic material.

8. "How Do You Like It," Keith Sweat Featuring Left Eye

It's always strange the first time one member from a group appears on someone else's song. Left Eye makes sure to shout out T-Boz and Chilli on the track -- they're even in the video, but blink and you miss them -- yet this track is all Miss Lopes. She helps Keith Sweat craft quite the nasty little cut all about the usual grinding Sweat was known for. Left Eye slams the gavel down though when she says, "And as we come a little closer to the end of the game, you know I'm takin' all the 'Sweat' out your name."

7. "Only You (Bad Boy Remix)," 112 Featuring Notorious B.I.G. and Ma$e

In 1996, Puff Daddy was on the brink of something major with Bad Boy. Notorious B.I.G. was already a household name, Ma$e was right behind him and 112 provided the melody for it all. "I thought I told you that we won't stop," Puff chants at the beginning of this remix. While 'Only You' hit hard on so many levels with 112's ability to be sweet and party-poppin' at the same time, it's hard to ignore the sentimental value of Bad Boy's burgeoning empire on this one.

6. "Let's Get Married (Remix)," Jagged Edge Featuring Run-DMC

Run-DMC had a knack for taking one song and melding it with another -- remember the Aerosmith-assisted jam 'Walk This Way'? When they entered on the remix to 'Let's Get Married,' Jermaine Dupri sampled Run-DMC's classic 'It's Like That' and three the hard way took the ball from there. Having a legendary rap group on your track's remix was a big deal at the time -- and it still is. Thankfully having Reverend Run on a track took away from the far from romantic line on the song, "We ain't gettin' no younger. We might as well do it" -- aka the lyrical equivalent of a Kanye shrug.

5. "I Wanna Be Down (Remix)," Brandy Feat. MC Lyte, YoYo & Queen Latifah

Brandy was just starting to get her sea legs in R&B when she came through with her debut single 'I Wanna Be Down.' The R&B princess took it to another level by corralling some of the hottest female MCs in the game and putting them on her remix. The soft lighting of the video was a stark contrast to the hard-hitting rhymes these females were delivering. Fast forward about 17 years and Brandy's rap alter-ego Bran Nu could've joined them in the rhymes.

4. "Can't You See," Total Featuring Notorious B.I.G.

Total's breakout 1995 hit "Can't You See" features an infectious sample of James Brown's "The Payback" and a cameo verse from the late Big Poppa.

3. 'Anything (Remix),' SWV Feat. Wu-Tang Clan

This slam dunk song off the 'Above the Rim' soundtrack was just what that era needed. SWV were the around-the-way girls who wanted to fall in love, but also have a good time. The Wu were a couple of booksmart street hustlers from Shaolin, who on the low wanted the math to work with their "wisdom." Together, it was an all-around hit, and who could forget Method Man's idyllic way of making his presence felt: "Kaboom! Guess who stepped in the room? Ticaaaaal!"

2. 'Fantasy (Remix),' Mariah Carey Feat. Ol' Dirty Bastard

When Mariah Carey interpolated the bridge to Tom Tom Club's 'Genius of Love,' -- along with sampling the instrumental -- she had to know she had a hit on her hands. She stretched the 'Fantasy' even further when the late Ol' Dirty Bastard jumped on the track. Everyone under the sun impersonated ODB on his opening bars, spitting, "Me and Mariah, go back like babies with pacifiers. Ol' Dirt Dogg no liar. Keep the fantasy hot like fire."

1. 'I'll Be There For You/You're All I Need To Get By,' Method Man Feat. Mary J. Blige

Sure, this top track totally reverses the entire point of this list, as it's a singer assisting a rapper. However, excluding this song from the list would be a sin against society. Method Man and Mary J. Blige took a simple track off Meth's solo debut album and reworked it into the epitome of hip-hop Love. It's like 'Brown Sugar' in song form, where two people from different (yet similar) walks of life fall in love. Some couple played this song at their wedding in the '90s. They had to.

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