VCO with range of 0.2 Hz to 27.0 Hz
If you still want a VCO, you can try this super-easy circuit: 



Since you want a very wide range of VCO frequency, use a 2N7000 rather than the BJT and increase C to around 0.27uF assuming 5V supply. Values will be a bit different if you use another type of op-amp and a lot different if you use a different supply voltage. 

That should give you 0.2 ~ 27Hz for control voltage in the 0 ~ 5V range.  

That said, I don't know if I'd let a stepper anywhere near a turntable, even with very rigid construction and microstepping.