The best thing about having the Roots as your house band is that they can play anything at the drop of a dime, allowing for some entertaining impromptu jam sessions. When Weird Al visited Late Night with Jimmy Fallon a few weeks ago, Questlove recorded a quick cover on his phone of Madvillian’s “Accordion,” officially spawning one of the unlikeliest covers in hip-hop history.

Summarizing hip-hop’s musical history itself, though, is a task that requires much more practice. Jimmy Fallon and Justin Timberlake recently performed “History of Rap Vol. 2,” once again instigating curiosity about the rehearsal hours needed to pull it off so flawlessly. Just like their first rendition, the second episode is a fast-paced journey of memorable hooks, verses and jives from rap’s growing vault of classic songs, from Kurtis Blow all the way to Cali-Swag district. Highlights include an impressive auto-tuned duet (did they filter the mics?) and Fallon being overwhelmed by the intensity of Rick Ross’ “B.M.F.” Free talk show promo is an easy plug, and with Timberlake now taking Myspace under his wing, the third installment might come sooner than expected.