The whole song just repeats a 4 measure chord progression of Bbmaj7, Cmaj7, and Ebm.
 
 Bbmaj7 Cmaj7 Ebm
|--5-----7-----6--|
|--6-----8-----7--|
|--7-----9-----8--|
|--8-----10----8--|
|-----------------|
|-----------------|

               Bbmaj7
Uh, was always smart-mouthed and quick-witted
                         (Bbmaj7)
But somethin' was always missin' like six digits
                     Cmaj7
Lucky seven probably poppa
                     Ebm
Little nigga so they picked on him, hassled him
Bbmaj7
Things changed when I hassled back, so
      (repeat)Bbmaj7
David hit the...


The trumpet is only playing the arpeggio of each chord.
and that's it.