where to add gain and volume controls to LM386 guitar amp circuit?
If your are talking about the "loudness" of the audio signal coming out of your speakers then gain and volume are the same.Simplified: gain is a technical term how much a signal is amplified. Thus a gain of 10x means the output signal is ten times larger then the input signal. A gain of 0.1 means output signal is ten times smaller then the input signal. The more 'gain' the 'louder' the music.If your are dealing with music it is normal to have the same 'gain' but in order to control the volume, you somewhere in the system make the signal amplitude variable between 0 and max. (As your hearing is logarithmic you use a logarithmic variable resistor). With the volume control you make a variable 'gain' between 0 and 1. Lets say your amplifier has a total 'gain' of 10.000. What you do with the variable resistor is you make the input signal smaller. If we make it 1000 times smaller. That is a gain of 1/1000. the 'gain' of the whole system is 1/1000 * 10.000 = 10. If you turn your volume completely down the gain is 0. That gives 0 * 10.000 is a gain of 0. (No amplification which should be silence but you will still hear noise. Let's ignore that). If you turn the volume control to max the 'gain' of the system is 1 * 10.000 is 10.000.The answer to your question is that you can NOT change the volume and not the gain or vice versa.


  I want to be able to get the distortion and clipping of high gain but at a low volume.


Straightforward hard 'clipping' is simple using .e.g. a set of diodes but I assume you want to keep the 'volume' the same and variable the amount of clipping. In that case I suggest you look for a good circuit using the www. because it is a bit beyond the scope of 'stackexchange' to make a  design for you.