They're often shabby, beat-up instruments - but from time to time someone sits at a street piano, and something extraordinary happens. Here are a few of the best.
Self-taught child plays Chopin at St Pancras
Jay Lewington, who is reportedly self-taught via YouTube tutorials, plays Chopin's Fantaisie-Impromptu at London's St Pancras International station. Neither the bustle of passing travellers, the screaming of a baby, a crying bystander, nor a safety announcement can put the eight-year-old off his stride.
A street piano, a music lover and two million likes
A video of a homeless man playing a street piano in Sarasota, Florida is now one of the biggest things on the internet. The footage of 51-year-old Donald Gould's piano arrangements has now gone viral, as well as a video of Gould speaking to the media about his love of music and his past musical education. Offers of support have flooded in for him – there's even the possibility of work in a piano bar. The power of music, and the power of the internet, it's an amazing thing.
The homeless man with the unexpected talent
After living on the streets of Alberta, Canada for 30 years, Ryan Arcand learned a thing or two. But, most importantly and movingly, he learned to play the piano as well. The piano may need a tune, but his honest playing certainly doesn't.
An amazing 11-year-old plays Liszt
Wowing passers by in Cambridge with effortless cascades of romance-laced notes, this kid's got some talent. (his name's George Harliono - and very much one to watch)
Prague's pianistic policeman
High-vis jackets are often recommended, especially if you should need to spot your soloist from a great distance.
Full-body virtuosity in Paris
The French capital has its share of street pianos too - and this guy has the notes (and the moves) for a virtuosic display par excellence.
Inspirational improvisation at Venice Beach
A homeless man stuns with his keyboard mastery in his Baroque-infused rhapsody.
An impromptu boogie-woogie show
Some passengers at St. Pancras station were clearly thrilled by this commuter hybrid of Jools Holland and Richard Hammond, some were more concerned with the departures board. Oh well, can't win them all.
One of the world's great pianists
No Royal Festival Hall for Valentina Lisitsa - all this star with 70 million YouTube views needs is a battered piano and an audience.