Sumer is Icumin In

This is the oldest known musical composition featuring six-part polyphony.  Apparently it also may not be entirely appropriate for today, as "Sumer" may have applied to a longer period of time than "Summer", and so they may have been singing this earlier in the year in the 13th century.  Regardless, here's hoping for a Summer as festive and merry as this rendition of a very old song.