A title, introductory to the 45th and 69th Psalms. A marginal note says of this word, "that is, Lilies." The indication is that Shoshannim was a formal direction to the choirmaster or leader of the music, as to the tune, tempo, quality, or the instruments to be used as accompaniments.
Meta. The idea here is beauty and purity of thought and feeling (lilies) as a factor in bringing about harmony, music, orderly and melodious ideas, and their expression in mind and in body (trumpets bespeak giving expression to).