The organ is called a tymbal. On each side of the first abdominal segment sits a stiff, corrugated membrane attached to a large muscle. When the muscle contracts, the ribs buckle in sequence with an audible click, and the plate springs back when the muscle relaxes, producing another. Repeated hundreds of times a second, the clicks fuse into the continuous song.
Most of the male abdomen is a hollow air sac that resonates, and the song is radiated through thin tympanal membranes. The result is among the loudest sounds made by an insect, with several species exceeding one hundred decibels close to the animal.
A calling male has to protect his own hearing, and does so by creasing the tympanum during song. Females of most cicadas do not sing at all, but in many groups they answer with a timed wing flick, and the male homes in on that reply.