I picked the usual walking bass line that you hear in jazz music-- though I actually played it with a piano. My objective was to keep the listener genuinely interested in the piece until the end. The introduction doesn't grab attention, but the momentum of the piece is actually created by the chord progression itself (AABACBA) The line doesn't resolve until the end, so the listener feels compelled to wait and listen until the 16 bars are over.
It's interesting that, throughout the piece, you can hear a distinct change in volume on certain notes. I'm not entirely sure if that's because I pressed a certain key harder, or if the pitch of the notes made them seem louder, but that was an interesting and unforeseen facet of this project.
I wasn't entirely sure how to upload the logic file, but I did upload a screenshot as a placeholder until I figure it out.
(I commented on the pieces of Francisco, Ivan, and Jeremy.)