I might be conflating this with another story from the book, but I believe Adrock says that he took some of that money to a shop intending to buy a guitar, changed his mind on the spot, and walked out with a Roland TR-808 drum machine instead. And that ended up being the drum machine he used to program the beat for "I Need a Beat" by LL Cool J, the first release on Def Jam.
― JRN, Thursday, 5 May 2022 16:14 (two years ago) link