That area of Southern California (LA Basin) is very challenging airspace. Both large, and very large airports, and numerous small airports as well as military. Compounding this congested airspace is a large amount of general aviation aircraft, as witnessed by the audio tape. The weather is usually very nice, which generates all the aerial activity. It is the only airspace that I fly in, where I’ll put the autopilot on ASAP because it’s vital to have eyes and ears open. I will always brief my F/O to keep any extraneous chatter to a minimum and make short, crisp, transmissions on the radio.