Exact what the title say

I know I have to change some caps, but wich caps?

Or I leave it "stock" and use it as it is

Thanks

On compressors in general, one usually has to set the attack/decay parameters to suit the range of the source and its normal envelope characteristics.  Rule of thumb is that things lower in pitch need a bit more rise and fall time.  You may want to play with the 10uf cap that goes between ground and the collectors of the two transistors and 150k resistor.  Bigger will make it slower.  Smaller will make it faster.  Slower wil smooth it out and reduce envelope ripple.