While I was not playing (not a very strong aptitude for instruments or sings well), I had a great experience in the town of Dingle in Ire. Sitting in a pub where a scheduled band had not arrived, there was a prontanious jam session. A local started playing the spoons. There was a family from Russia - the sun pulled out a violin and started playing like a true fiddle master. As the minutes went on, people ran to their cars to get banjo's, guitars, tin whistles, est.By the time the band showed up a couple hours later, it was a packed house and instead of "taking over" they just joined in the jam session.
One of the best nights of music I have ever experienced