The exercise this week is to take a bass-free backing track and construct
a bass line, instead of just noodling. Steve said something like,

   Pretend you want the job and a producer is listening to your work to
   decide if he wants to hire you. You should be able to justify your
   choices, not just "I fiddled around and this is what came out."

I took this backing track from youtuber "Quist":

    Funky Groove Bass Backing Track (Am), 5m15s
    https://www.youtube.com/watch?v=cqT4aERwFpk

It is just these four bars over and over:

    | Am  | D7  | Fmaj7 | E7 |


The game plan:

My approach was to play along with the track freely, develop a few
ideas, then play along with it a few more times limiting myself to
some of those better ideas plus small variations.

I did two takes once I had the ideas generally set. I didn't write
anything down, so my timing isn't great because I'm thinking about
what I'm playing and playing next, not just reading or playing from
memory.

It is hard to keep it interesting without getting too busy, since it is
just four bars repeated over and over.

Summary of what I did:

   - start simple, then embellish

   - save the greatest variation for the transition back to Am

   - first round: sit out

   - second round: just punctuate the root on 1

   - third round: introduce the simplest version of the main riff,
        still somewhat staccato

   - fourth round: repeat the 3rd round, but less staccato and flows better

   - next two or three rounds: same as fourth, just doing slight variations,
        mostly on the E7 -> Am transition

   - the break comes (2:40). everything in the backing track is pared back,
        which means I need to introduce something new, so I change the
        main riff to drop down and climb up instead of just just climbing
        up from Am to D7

    - after the break, continue on with the idea from before the break,
      but allowing myself more latitude for small variations and mixing in
      the new idea from the break when I feel like it

    - I had intended to simplify and fade out in the last round, where each
      measure is just the root note followed by quieter echos of that note.
      But because I couldn't see the whole wave on screen, I jumped the gun
      and changed to this idea one round to early, so I just kept on with the
      idea to fade out.