There are 270 London Underground stations, but only 65 of them play music - specifically, classical music.
It may seem a bit of an odd choice, but in fact it was a decision made for a very smart reason - it's been shown to help stop anti-social behaviour.
Other train stations across the UK also use the technique, as do some McDonald's, as it's thought to discourage young people loitering around and causing trouble.
But not all 65 of the stations that play music today were picked because they had trouble with anti-social behaviour, some just liked the idea so much they jumped on the bandwagon.
These are the 65 Tube stations where you'll hear classical music:
Chalfont and Latimer
Elephant and Castle
Great Portland Street
Harrow on the Hill
High Street Kensington
Shepherds Bush Market
Photo credit: Kirsty O'Connor/PA Wire