Across Britain, 352 BBC transmitters stand, mostly on the tops of hills broadcasting sound, music and voices invisibly across the country. In this slow radio episode, Matthew Herbert and a group of recording engineers visited some of these transmitters in Scotland, Wales, Northern Ireland and England to listen to what the transmitters were hearing at exactly 11.30 at night - the time of this broadcast. Starting at the transmitter atop Crystal Palace and then moving through the country to finish in snowy Aberdeen, hear how the sonic landscape changes the further north travelled.

Transmitter is a production from Munck Studios with Matthew Herbert for BBC Radio 3, recorded by Pete Stollery, Hugh Jones, Dan Pollard, Ella Kay, Robbie McCammon, Pieter Dewulf and Cameron Naylor.