So you’re on the Metro, reading the paper or staring out the window, deep in your own thoughts. Suddenly, your mellow is harshed by the annoying plink of someone trying to play “I’m Yours” on a lavender ukelele. Okay, so maybe it wasn’t quite that bad — photographer Paul Sharratt provides no editorial comment — but how would you react to someone strumming a stringed instrument on your train?