When an artist performs their own lyrics over the beat and melody of someone else's song.
Like cover songs, the songs that are most often freestyled over are hit songs of any genre, although mostly (for the reason above), hip-hop, R&B, and pop songs.
This is not always the case however, and it is not uncommon for a more popular artist to give an unknown a Colbert Bump by freestyling over their song.
This is also related to Battle Rapping, though it's much more competitive than typical freestyling.
The legality of freestyling is in a similar area to the legality of Sampling, which can be viewed at that page.
Note that it's possible for a song to be a freestyle over an original beat — a freestyle traditionally refers to a rap song that doesn't use conventional song structures (e.g. no hooks) and aims to display the emcee free-associating with their typical subject matter. Often, pre-existing beats would be used for this, so the term is now applied to Freestyle Version songs as well, even if they use hooks and song structure. Also, a song being a freestyle shouldn't mean it's improvised — the majority of freestyles are pre-written, or occasionally made up of pre-written lines combined improvisationally. Fully-improvised lyrics are also called "off-the-dome" or "off the top" freestyle, which is virtually impossible to master; even many great rappers struggle with it.
- Lil Wayne built a lot of his buzz off of this. His Dedication series of mixtapes uses this trope almost exclusively, freestyling over the popular songs whenever the mixtape is released, as does his Da Drought series, and almost every other mixtape he's ever released.
- Kanye West recorded a freestyle over his One-Hit Wonder Rich Boy's "Throw Some Ds", which turned a song about money and cars into a song about breast implants.
- Around a quarter of Drake's mixtape So Far Gone is freestyles, using songs by Jay-Z ("Ignorant Shit"), Kanye West ("Say You Will"), Lykke Li ("Little Bit"), Santogold ("Unstoppable") and Peter Bjorn and John ("Let's Call It Off").note
- Rick Ross' 2012 mixtape The Black Bah Mitzvah which was entirely composed of freestyles over popular songs at the time - although after Ross had done his freestyle verse, he let every song play out as it originally was, causing lots of Epic Rapping, which for many was divisive.
- Kendrick Lamar freestyled over Kanye West's "Monster" in 2010 and created a brilliant Villain Song out of it.
- Femcee Nitty Scott (who has collaborated with Kendrick Lamar) freestyled over "Monster" and the video of her doing so went viral and kickstarted her career.
- Nicki Minaj has done a few of these, over songs by Jay-Z ("Encore"), The Notorious B.I.G. ("Warning"), and also PTAL's "Boss Ass Bitch".
- Frequent across J. Cole's earlier mixtapes, mostly over songs by Kanye West and Jay-Z (notice a theme here?), although also over Cassie's "Must Be Love", Missy Elliot's "Best Friend" and Talib Kweli's "Get By".
- Busta Rhymes does freestyle versions a lot, for instance over such songs as Kendrick Lamar's "Backseat Freestyle" and "Poetic Justice" and Drake's "Best You Ever Had".
- Lupe Fiasco freestyles often on his mixtapes. In Friend of the People, he freestyles over obscure dance and dubstep instrumentals and also over John Coltrane's A Love Supreme. He also freestyled Que's "OG Bobby Johnson" as "THOT 97".
- The Weeknd did a freestyle version in 2014, freestyling over Lorde's "Royals", Ty Dolla $ign's "Or Nah" and Beyoncé's "Drunk in Love" (although he significantly altered the beat for this one).
- Azealia Banks freestyled over "Harlem Shake" when that song was popular.
- Van Morrison tends to this when he does a cover version. His cover of It's All In The Game starts out as a conventional version sticking more-or-less to the official lyrics, but by the end it has diverged so much that on the Into The Music album, the second half of the cover is listed as a seperate track and given a new name (with songwriting credits for the lyrics given to Van).
- One famous case is when Paul Anka adapted Comme d'Habitude for Frank Sinatra as "My Way". The only thing the two songs hold in common is the tune.
- The end credits song of the English dub of Pokémon: Jirachi: Wish Maker is "Make a Wish", a remix of the original Japanese ending theme, Asuka Hayashi's "Chiisaki Mono" (A Small Thing). "Make a Wish" has the same overall tune as "Chiisaki Mono", with half of the lyrics replaced with English-language ones.
- Juice WRLD did an entire freestyle set using exclusively Eminem instrumentals - in return, Eminem gave him a guest feature on one of his singles ("Godzilla"). (Juice's death happened before he could finish recording the feature.) Juice had a particular affinity with Eminem beats, and had a posthumous hit with "Doomsday", a freestyle he did with his friend Cordae over the beat to Eminem's 1999 single "Role Model".
- Eminem, known for his finnicky taste in beats, rarely raps over other rapper's beats unless he produced them himself, but has an interesting example in his late career: The first beat for his 2020 track "Book Of Rhymes" is the beat for "Talk Shit Like A Preacher" by Future, sped up a little. This came about because the beatmaker, ATL Jacob, gave the beat to Future for $10000, and got no response, assuming Future had discarded the song. Later, Eminem and Dr. Dre called and asked him if he could use the beat, paying $30000 for it. A few months later, Future told ATL Jacob he was going to use the song with his beat on his album. Jacob, out of loyalty to Future, let Eminem know what had happened and attempted to return the money, but Eminem wasn't bothered and worked it out with his lawyers. Future has a writing credit on Eminem's eventual "Book Of Rhymes".