you should use a logarithmic line~ object to adjust the curve as smooth as you want.
On top of that you should apply a Nyquist correction to the output of your oscillator abstraction.
So here you have some imagines how to do that. The Nyquist abstraction is used in the output of the triangle oscillator abstraction as an example. Then the final output can be controlled with a logarithmic line~ object.
OBS : If you need more then one oscillator you can apply this for each oscillator and then use a mixer and then the output of the mixer you use again the same idea. In this way you have an oscillator smooth stage control and a final mixer stage control for extra smoothness.
This is just the simple mono smooth control (no curve adjustment)
The same idea but as a stereo version
Here is with logarithmic smooth control (with curve adjustment)
Here you have a Nyquist correction abstraction
Here you have a triangle oscillator with Nyquist correction
You can also download xline~ which is an object that is doing just that :