In May, 1998, Rawkus Records released Lyricist Lounge, Vol. 1. The double-album featured a host of great artists, including De La Soul, Kool Keith, Q-Tip, O.C., and Bahamadia. Notably, the Top 200 charting release also included El-P, who with his Company Flow cohorts, J-Treds, Queen Heroine, and The Juggaknots was part of The Indelible MCs on “Weight.” Additionally, Rage Against The Machine’s Zack De La Rocha appeared, alongside KRS-One and a pre-Aftermath Entertainment tenured Last Emperor, on video single “C.I.A.” The latter song was perceived to hint at Zack’s long-touted solo album with Hip-Hop focus, featuring production by DJ Premier, DJ Shadow, Nine Inch Nails’ Trent Reznor, El-P, and The Soulquarians’ James Poyser. Of course, none of this music ever surfaced.

In the year that followed, Zack, who was simultaneously recording The Battle Of Los Angeles with R.A.T.M., reportedly lived in Fort Greene, Brooklyn with Co Flow’s El-P. El, who was on the fringes of leaving Rawkus to start his Def Jux imprint, was a veteran MC/producer in the New York City underground. For a reported one month, the pair recorded extensively. None of that music ever saw the light. El-P revealed this to NME:

“In 1999 I spent a month in my apartment in Brooklyn with Zack De La Rocha just before he split Rage Against The Machine, working on music that will never see the light of day. I can’t speak about his future but I will say that I’m going to L.A. to spend another month with him in January.”

This is exciting news for Zack Heads and El Heads—even if both Rage Against The Machine and Company Flow have become festival reunion acts. The pair (along with Killer Mike) worked on RTJ2, Run The Jewels’ recently-released sophomore album.

Read the full NME Run The Jewels feature, which also includes confirmation of RTJ3.

Related: Run The Jewels’ Blitzing Single Hits The Eyes As Hard As The Ears (Video)