Wonderful (planned) musical incidents in real-life places brought to light by WQXR new York … their “Q2” music by living composers is a treat! Listen and/or donate to WQXR to keep them going. This article has to do with their annual “High Notes and Low Tones for Classical Music in 2013” awards which led me to review some videos of music-related flashmobs. This was under their Frequent Flier Upgrade section in which players from the Philadelphia Orchestra performed onboard a flight before takeoff. More and more orchestras have blogs and other ways to keep in touch.
Philadelphia Orchestra in China (also see at WQXR)
Bucharest Symphony Orchestra at the airport
This one by my favorite group Improv Anywhere
And then if you follow suggested YouTube links, you see a lot more of this type of stuff