The microphone of an FM transmitter:

A microphone functions as an acoustic-to-electric transducer regardless of the type of transmitter (FM, AM, or SSB) it is attached to. It operates by capturing variations in air pressure caused by human speech or other sounds and converting them into a corresponding electrical voltage. There is nothing inherently unique about the physical microphone used for FM compared to other modes. It does not necessarily have a wider frequency range, a different tone, or a quieter operation simply because it is used for FM. The key principle is the basic physics of the device: sound waves (air pressure changes) move a diaphragm, which in turn generates the electrical signal that the radio will eventually amplify and transmit.