The first day of summer in Paris changed in 1982. The Fête de la Musique was born. After 29 years, the event does not show a wrinkle; it gets better with time. June 21 is a Monday in 2010. The streets are not as packed as when the date falls on a weekend. Rue Saint-Sabin, however, is jamming with a DJ and we are forced to reach Boulevard Richard-Lenoir via rue Sedaine. Any of our detours are not a problem because music is on practically every street in the neighborhood. When you visit Paris on June 21, you can try to get into the events at Palais-Royal, Musée d’Orsay or…