Hi there, It means that the speech was made in a lively, interesting, engaging and merry manner. Example: We had a light-hearted laugh when we saw our puppy chasing its own tail. Just to complete the discussion, we do something with a "heavy heart" when we are feeling sad/melancholic. Example: It is with a heavy heart that I announce the passing of our school Principal this morning. He was involved in a car crash and was killed immediately. Hope this helps. Cheers, Lance