All airports of my experience (not LTMA) seem to operate in a generally similar way to that described by ATCO1979 above. The Approach controller does the approach functions of VFR stuff, oubound releases when required, initial vectoring and sequencing of inbounds etc etc, and has overall executive responsibility for the approach control tasks. "Director" purely works the final part of the radar sequence. Very useful to share the workload when it's busy and you're trying to judge the final turn-on to the ILS to fine tolerances. Using two frequencies keeps the R/T loading down, which is good for everybody.