We've all experienced the moment - you're walking down the street minding your own business, or waiting to catch a train, and a street musician catches your ear. So you stop, and listen, and you're blown away. And there's great pleasure in that - in realising that total unknowns, and often amateur players, can be as brilliant as your favourite recording artists.
Maybe you take out your phone and post some footage online. That happens a lot, and sometimes the video goes viral. Here are seven times when that deserved to happen...
The piano man in Manchester
We'll start with the most recent example - of a pianist who casually started playing on a piano outside Forsyth Music Shop on Deansgate, Manchester earlier this month. It's not clear whether he's busking for money, or just having a jam, but he wows passers-by with an incredible medley of tunes ranging from rave classic Insomnia by Faithless to Dr. Dre's g-funk banger Still D.R.E.
As BBC Music News Live reported, the pianist was identified as Christopher Scamp from Liverpool, who told the Manchester Evening News: "I can play a few hundred songs and I can do them all the way through but tend to just mix parts of them together as not everyone has the patience for a full song."
The footage was captured by Manchester local Richard Parker, who shared his video on Facebook, where's it's already clocked up more than 6m views.
New York subway legends, Lucky Chops
There are tonnes of clips online of this incredible jazz-funk group, who usually play on the New York subway, although they've been filmed elsewhere, including on the Mexico City underground. They're called Lucky Chops, and they're both a street and professional band (the observant among you will have spotted dancing baritone saxophonist player Leo P performing at this summer's Beneath the Underdog: Charles Mingus Revisited Prom).
This medley of Lipps, Inc.'s Funkytown and James Brown's I Feel Good is something of their signature jam, and we couldn't agree more with the comment under this footage from 2015: "DUDE!! How can all those people just STAND THERE!??!"
The spirit of Hendrix on the streets of London
Hendrix lives! Or, his spirit does in the extraordinarily talented Lewis Floyd Henry, who plays covers of his hero on Brick Lane in London, and also has a fine line in melding rock and hip hop. As with Lucky Chops, there are plenty of clips of Lewis online, including superb mashups of Motörhead's Ace of Spades and The Notorious B.I.G.'s Juicy, and The Beatles' Helter Skelter with Dizzee Rascal's Fix Up, Look Sharp.
Three random guys sing together
And here's proof of the power of music to bring total strangers together. The man who shot the footage, Jaime Tatos Maldonado, explained on Facebook what happened: "I was walking to [an American supermarket] and saw this guy [Jesse Rya] playing a song. It sounded good so I decided to record it. By the end of the song three guys started jamming. This truly is music in its simplest form."
Amen to that. The clip went viral, and led to the Texan trio - wearing exactly the same clothes - performing the song on Jimmy Kimmel Live, complete with a more-established trio (of superstars): Trey Songz, Juicy J and Aloe Blacc.
A gorgeous cover of Ed Sheeran's Supermarket Flowers
Irish singer Allie Sherlock often sets up on the street in Cork and sings covers, and this is the one that went viral - a cover of Ed Sheeran's Supermarket Flowers, which Allie sang when she was just 12.
"I don't want it to be a professional career but I'd like to do it, just as a hobby," she told the Evening Echo. "I'd like to do childcare because my auntie owns a creche. I want to keep practising all the time and singing and so it's like a hobby, really."
Tragically, she also revealed to TV3 show Sunday AM that her online fame had caused trouble at school. It led to her being bullied, resulting in Allie leaving and being home-schooled.
Rotherham lad, 15, stuns locals in Doncaster
Here's another youngster with a big talent - 15-year-old Alfie Sheard from Rotherham who busked Tracy Chapman's Fast Car in Doncaster, and promptly got flown over to America to appear on The Ellen Show. There was a surprise in store for Alfie - Ellen had arranged for Ed Sheeran to film a message for Alfie, and he also gave him one of his guitars. Alfie: "Oh my days!"
Hallelujah on a Saturday night in Leeds
And we'll finish in Yorkshire - on a Saturday night in Leeds city centre and a duet between two local singers Jade Helliwell and Dawid Osial. Their cover of Leonard Cohen's Hallelujah went nuts on Facebook, clocking up more than 20m views.
Jade was on a night out and simply rolled up to Dawid and sang the song with him. The clip was such a hit that Jade quit her day job as a teaching assistant and began a career as a professional singer, as the Yorkshire Evening Post reported.