The microphone converts sound pressure wave to electrical signals.
These audio voltages are amplified by the audio amplifier.
The amplified audio is used to control the deviation of the frequency controlled oscillator.

The oscillator frequency is at the carrier frequency, in the 88-108 MHz FM band.

The low power of the frequency modulated carrier is boosted by the Radio Frequency amplifier.

The aerial is driven by the amplifier and produces an electromagnetic wave.

Under normal conditions the transmitted signal will travel as far as the horizon.