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:
Balham
Barbican
Barons Court
Bayswater
Becontree
Blackhorse Road
Bond Street
Bow Road
Brixton
Burnt Oak
Chalfont and Latimer
Charing Cross
Clapham Common
Clapham North
Clapham South
Croxley
Dagenham East
Dagenham Heathway
East Ham
Eastcote
Elephant and Castle
Elm Park
Euston Square
Fulham Broadway
Goldhawk Road
Golders Green
Goodge Street
Great Portland Street
Hammersmith
Harrow on the Hill
High Street Kensington
Hornchurch
Kilburn
Kilburn Park
Latimer Road
Leyton
Manor House
Morden
Newbury Park
Oueensway
Oval
Pimlico
Plaistow
Ravenscourt Park
Rayners Lane
Seven Sisters
Shepherds Bush Market
Sloane Square
Stockwell
Tooting Bec
Tooting Broadway
Tottenham Hale
Turnham Green
Turnpike Lane
Upney
Upton Park
Uxbridge
Vauxhall
Warren Street
Watford
West Brompton
West Hampstead
Wood Green
Woodford
Photo credit: Kirsty O'Connor/PA Wire