there isn't really much to say about this circuit as it is mostly a 8038 based function generator with a few bits added on such as a DC-DC convertor for the bi-polar power supply and a range/shape selector switches etc.
the ICL8038 is rated to range from 0.0001Hz to over 300KHz however the sine on the one I built up stops becoming useful at about 300KHz and it starts at about 10Hz however this maybe because I exclusively use parts from broken stuff - the IC was harvested from a PEAVEY classic chorus amplifier that died years ago, The pots came from an old mixing desk and so on so you may get closer to the rated range however 10Hz to 300KHz is fine for most if not all Audio applications.
I should also mention the LT1054 DC-DC converter, I got this as a free sample from Linear Technology and I used this over the more common MAX1044/7660 ICs because I need 12+/- volts and the 1044 has a maximum rating of 10 volts.
Notes:
The ICL8038 does get quite hot
Make sure the capacitors are all rated at 35volts or above
