This "Chicago Piano" had eight 40 millimetre machine guns grouped together and coordinated to fire in a specific pattern. It had a crew of at least eight men, one man each side to load the eight breaches, two men as Ammunition supply. Two men with large metal rakes, (as in garden,) to rake the spent brass casings, that were being ejected at a tremendous rate, to a safe area to cool down before being bagged and eventually stored, to be recycled eventually, ashore.
The" Chicago Piano" was controlled by a direction finder the latest technology at that time, this required a crew of four men, one of them being the Captain of the gun, a Trainer, a Layer, and a range coordinator. When an aircraft was picked up on the radar screen operator who was situated down in the bowels of the ship, the details of its position relative to ship, was relayed to the repeat dials on the direction finder, on the upper deck. The Trainer, Layer, Range coordinators' jobs were keep their dial pointers in line with the dial pointers being relayed from the radar control operator. When all the information had been correlated the Captain of the gun stood on the trigger foot pedal The gun started firing causing the deck to vibrate, it was like riding a very fast motor cycle over a very badly cobbled road. It was compulsory to wear earplugs as the noise was deafening, also anti flash head masks as protection against burning cordite being expelled from the 6-inch guns after firing. The Pom Pom shells would exploded on impact or at their extreme range. If you were to look, up at the target area you would see a large area of smoke from the exploding shells, in the shape of a three-dimensional square. The object was to place this barrage in the path of the enemy aircraft. Once on target very few aircraft survived the barrage of 920 rounds of high explosive/armour piecing/incendiary rounds every minute. It was an exhilarating feeling of power, and an awesome experience. The range of the 40 millimetre shells was 3500 metres, at 45-degree angle.