That's what the film seems to suggest. That he didn't write anything down and the whole thing was done in one cut/take. Well to me it really seems highly unlikely. The song is just too damn perfect.
shareBiggie is known for not writing his raps down, keeping them all in his head. Who knows if he freestyled it, but I doubt it. He, along with other artists, do all their writing within their minds. Brother Ali, Jay Z and Mac Lethal are others known for doing so. There's no way to really answer your question because BIG is the only one who could answer that factually.
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The more you know who you are, and what you want, the less you let things upset you.
Not sure if it was freestyle tho but it was In just one take..
This is for Allah... and it's going way out there sucka...
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I think you've got the term "freestyle" wrong. A freestyle doesn't have to be improvised.
Also it doesn't make someone a bad rapper if they can't rhyme off the top of their head.