The John Dory, Zeus faber, has a pair of intrinsic sonic muscles on the swimbladder wall and produces sounds by rapid contractions of the muscles. The physical properties of the sounds and the detailed innervation pattern to the sonic muscle were investigated. The dory emitted two types of the sounds: ‘bark’ and ‘growl’. The bark consisted of continuous multiple pulses and lasted about 85 ms on the average. The growl consisted of a group of intermittent single-pulses and lasted for 50 ms to 1·2 s. The main frequencies of both sounds were almost similar and ranged between 200 to 600 Hz. The sonic muscles were innervated by the sonic branches of the first to fourth spinal nerves. The innervation from the first spinal nerve was newly revealed in the present study. A total of 1700 myelinated axons innervated the sonic muscles on both sides. There were no sex differences in the sonic muscle size as judged by the sonic muscle–somatic index (male: 0·675%, female: 0·670%).