For most audio line stages, I have not found it necessary to isolate the analog and digital sections. Usually I just do a ground plane on the back side of the PCB, trying to do as much of the routing on the front side as I can. If I end up with a lot of porosity in the ground plane on the back, then I may be inclined to add a front ground plane as well and stitch the two together with a bunch of vias.
Couple design suggestions you may consider...
The TL072 is an old and venerable chip, but it has high input voltage noise and poor current drive capabilities. For a line stage, the input voltage noise is not likely to be a big deal. It's more of an issue in a mixing console where it does start to add up. Of bigger concern are load driving capabilities. I'm not sure what the output of this is driving, but if it's going to be driving your RCA outputs then I'd strongly suggest replacing the TL072s in the tone control circuit with something that can drive lower impedance loads without high distortion. The OPA1642 and especially the OPA1656 are great choices in this regard, though they are only available in SMD packages.