This is an amazing project from Sam Isenberg:
It uses Markov chains and a huge data set Sam scraped to generate rap lyrics (as well as lyrics for other genres). There are some hilarious examples of the tool's output over on r/hiphopheads.
Sam studies Data Science & Analytics and has a great breakdown of the project on his site including more technical details about Markov chains and the markovify tool.
His breakdown also talks about some features not included in the released version of SongwriterBot, like the entertaining ability to combine the data to create “Harry Potter” x “Rap” generations.