Since the tempo slot in DefScore only takes integers, what would be the best way to get a more natural playback tempo?
I'm using this method now but it doesn't sound very smooth. 

(setf tempo-4 (make-tempo (vector-round 58 61 (gen-white-noise 12)) left :type :length)) ;Left is the output of an assemble-seq

I've also tried things like this:

(setf tempo-2 
      '(("Mixed Tempi" q :accel 60 62 1/32 2)
        ("Mixed Tempi" q :accel 62 60 1/32 2)
        (:rit 60 64 1/32 12)))

But most of it sounds either too intentional or too clunky, I just want the tempo to very slightly meander. Thanks in advance for the advice!

increase the step value to 1/128.